SACE Stage 1 Earth and Environmental Science · Topic 3: Processes in the Geosphere
Inside the Earth.
No borehole has gone deeper than about 12 km, yet we know the Earth has a liquid iron outer core and a solid mantle that flows. Work in a team, study the evidence, and work out the inside of the planet for yourselves.
How the lesson works
A · Reading rocks
Activities 1 and 2. How features of sedimentary rocks show where they formed, and how far the present can explain the past.
B · Inside the Earth
Activities 3 to 6. Seismic waves, shadow zones and meteorites, then the layers of the Earth to scale.
C · Heat and movement
Activities 7 and 8. Where the Earth’s heat comes from, and how it builds hot-spot chains and moves plates.
Show what you know
Screen 10. Nine questions, one for each I can statement.
How POGIL works
You work in a team of three or four. Each activity gives you a model to study, then questions that lead you to the idea.
Directed questions are answered from the model, convergent questions ask you to pull ideas together, and divergent questions ask you to go further. Agree on an answer before the recorder types it, then compare with the model answer.
Choose your team role
What we are learning
How geologists read the past from rocks, how seismic waves and meteorites show what the inside of the Earth is like, and how heat from inside the Earth makes plumes and moves plates.
I can
- 1explain how features of sedimentary rocks show how they formed, using uniformitarianism.
- 2discuss the limitations of uniformitarianism.
- 3explain how P and S waves show which layers are solid and which are liquid.
- 4explain how shadow zones show the layered structure of the Earth.
- 5explain how meteorites are evidence of what the inside of the Earth is made of.
- 6describe each layer of the Earth and how continental and oceanic crust differ.
- 7interpret a geothermal gradient graph and explain how radioactive decay heats rock.
- 8explain how a mantle plume makes a chain of hot-spot volcanoes.
- 9explain how convection, ridge push and slab pull move plates, and why oceanic plates are subducted.
SACE Stage 1 Earth and Environmental Science, Topic 3: Processes in the Geosphere. This lesson covers all four of the topic’s Science Understanding statements. The teacher notes at the end quote them in full.
My notebook
Team record
Three pages: team roles and a reflection for each activity, the key convergent questions with space for the team’s answers, a blank cross-section to label the layers, and tables for the Habanero gradient and the Hawaiian speeds.
AReading rocks
Activity 1: the present and the past.
How can ripples on a beach today tell us about a sea floor 550 million years ago?
Geologists cannot watch a 550-million-year-old sea or a 280-million-year-old ice sheet. They watch processes happening now, note what each one leaves behind, and look for the same marks in old rocks.
This activity · about 40 minutes
- Study Model 1 as a team, then answer questions 1 to 4.
- Study Model 2, then answer questions 5 to 7. Agree on each answer before the recorder types it.
- Use what you have worked out to match eight rock features to the environments that made them.
| What happens today | What it leaves behind |
|---|---|
| Water flows one way in a river or tidal channel | Lopsided ripples, with their “steepest surface facing in the direction of the flow” (Earle, 2019) |
| Waves slosh back and forth in shallow water | Symmetrical ripples, both sides at the same angle |
| Pebbles roll and knock together in a river or on a beach | Rounded pebbles: “The farther sediments are transported, the rounder they become” (Panchuk, 2019) |
| Ripples and dunes move along in a river or desert | Cross-bedding: angled layers, each one “related to a different ripple that advances in the direction of flow” (Earle, 2019) |
| Wet mud dries in the sun | Mud cracks, because the clay “tends to shrink on drying” (Earle, 2019) |
| An underwater avalanche of sediment slows down | Graded beds, “coarse at the bottom” and finer “toward the top” (Earle, 2019) |
| Water evaporates from a salt lake such as Lake Eyre | A salt crust; “The most crucial requirement for evaporite production is aridity” (Britannica) |
| A glacier drags rock across the ground | Scratches (striations) on the bedrock, and till: “a mixture of rock fragments and boulders in a fine-grained sandy or muddy matrix” (Britannica) |
Which feature in Model 1 tells you the direction a current flowed? Directed
A layer of old mudstone has mud cracks on its top surface. Was that mud under deep water when the cracks formed? Directed
Every row of Model 1 follows the same pattern. Describe that pattern in your own words. Convergent
Each row links a process that we can watch today to the mark it leaves behind. If we find the same mark in an old rock, we can infer that the same process happened when the rock formed.
Write the idea from question 3 as a general principle that a geologist could use on any rock. Convergent
The processes we see working today also worked in the past, so we can use them to explain what we find in old rocks. This is the principle of uniformitarianism, “in other words, the present is the key to the past” (Britannica). James Hutton presented the idea in 1785, and Charles Lyell spread it in Principles of Geology (1830–33) (Britannica).
Along the cliff tops are “polished and striated” rock surfaces and a layer of boulders in a muddy matrix, lying on rocks about 300 million years older (Preiss, 2019). National Parks SA calls the pavements “the best record of Permian glaciation in Australia”, “a record of an ice age about 280 million years ago”. The scratches show ice moving “toward the north-northwest” (Preiss, 2019). There is no ice at Hallett Cove today.
Some of Earth’s first animals lived here on the sea floor “more than 550 million years ago”, and the park protects “an ancient, fossilised seafloor” (National Parks and Wildlife Service SA). The rock surfaces have ripple marks: slabs of “ripple rocks of the ancient sea floor” were even used to floor the station’s woolshed (same source). Today the rocks lie in the dry Flinders Ranges.
The craters began as maars, “Small, low, open explosion craters”, and a “scoria cone” followed (South Australian heritage fact sheet). Geologists recognise these landforms by comparing them with eruptions watched today. Sources date the last eruption to “over 5,000 years ago” (University of Melbourne) or “as late as 4,000 to 4,300 years ago” (South Australian heritage fact sheet).
Which rows of Model 1 did geologists use to read Hallett Cove? What did they infer? Convergent
The glacier row. Modern glaciers scratch the rock they move over and leave till. Finding striations and till at Hallett Cove, where there is no ice now, means an ice sheet once covered the area, and the direction of the scratches shows which way it moved.
The Nilpena beds have ripple marks. What does that suggest about the sea the animals lived in? Directed
Suppose you find a ripple-marked bed tilted steeply on its side. Name two features that could tell you which way was originally up, and explain how. Divergent
Several features work. Graded beds are coarse at the bottom and fine at the top, so “the larger, older grains are at the base of the bed” (Newfoundland and Labrador Department of Energy and Mines). Cross-beds are cut off at the top of each set, so they show the bedding tops (same source). Mud cracks and raindrop pits form on the upper surface of a bed, and mud cracks narrow downwards. If any of these appear upside down, the beds have been overturned.
Apply it: what made each feature?
AReading rocks
Activity 2: how far can we trust it?.
If the present is the key to the past, what happens when the past was nothing like the present?
Uniformitarianism works because the laws of physics and chemistry do not change. But the rate of a process, and the conditions on Earth, have changed a great deal.
This activity · about 35 minutes
- Read the three cases in Model 3 as a team and answer questions 1 to 4.
- Read Model 4, about Pluto and Mars, and answer questions 5 and 6.
- Sort six inferences: safe to make, or needs care.
In the 1920s J Harlen Bretz argued that huge floods had carved the Channeled Scabland of Washington State. His idea was “rejected as not conforming to the current assumptions of uniformitarianism” (IUGS). Geologists later accepted that an ice dam holding back glacial Lake Missoula had collapsed at the end of the last ice age, more than once, releasing floods with about “ten times the flow of all the rivers in the world” (IUGS).
Banded iron formations “likely formed when Fe(II)-rich hydrothermal fluid wells up into shallow water”; the oldest known, in Greenland, are “3.7-3.8 billion years old” (NASA Astrobiology). Oxygen did not become a major part of the atmosphere until about 2.45 billion years ago (NASA Astrobiology). Romano (2015) notes that “some processes which are currently operating cannot be extended to the geological past and vice versa”.
Plants first “gained a foothold on land” in the Ordovician Period, 485 to 444 million years ago; the oldest spores, from 470 million years ago, resemble those of liverworts (Brooklyn Botanic Garden). Liverworts have no true roots, so for millions of years before and after this there was nothing rooted to hold river banks together.
What did Bretz’s critics get wrong? Directed
In each case in Model 3, what stayed the same as today, and what was different? Convergent
The physical and chemical laws stayed the same: water still eroded rock, iron still reacted with oxygen. What differed was the rate (a few enormous floods instead of slow erosion) and the conditions (an atmosphere with little oxygen, land with no plants).
Rewrite your principle from Activity 1 so it still works for all three cases. Convergent
The same natural laws and kinds of process operated in the past as today, but their rates and the conditions they worked under could be very different. Geologists sometimes call the first part actualism. Lyell had argued that causes acting today “had always been of the same magnitude in the past” (Darwin Online); that part has been dropped.
A geologist finds a river deposit 900 million years old. Why should she be careful comparing it with the Murray River today? Divergent
Before land plants there were no roots to hold banks together, so rivers may have spread and shifted in ways modern rivers rarely do. Water still flowed downhill and moved sediment by the same physics, but the pattern of the deposit could differ from any river today.
When New Horizons flew past, a sheet of ice “clearly appears to have flowed”, and “may still be flowing”, “in a manner similar to glaciers on Earth” (NASA). The ice is not water: the plain is “rich in nitrogen, carbon monoxide, and methane ices”, at about minus 234 °C. Its surface is broken into “icy, churning, convective ‘cells’”, “10 to 30 miles (16 to 48 kilometers) across” (NASA, 2016).
The Curiosity rover photographed rocks made of rounded pebbles cemented together. “The rounding indicates sustained flow,” said one scientist, and another said “These conglomerates look amazingly like streambed deposits on Earth” (NASA JPL).
Which row of Model 1 did scientists use to read the Mars rocks? Why does it work on another planet? Convergent
Rounding of grains. On Earth, “The farther sediments are transported, the rounder they become” (Panchuk, 2019), because grains knock against each other in moving water. The physics of abrasion is the same on Mars, so rounded pebbles there also point to flowing water.
Pluto’s glaciers are nitrogen ice at about minus 234 °C. Is it fair to compare them with glaciers on Earth? Give a reason for and a reason against. Divergent
For: the process is the same, a solid that flows slowly under its own weight, and the shapes on Pluto match flowing ice. Against: the material, temperature and gravity are very different, so the speed of flow and the shapes it makes may not match Earth’s exactly. This is the same idea as question 3: same process, different conditions.
Apply it: safe, or needs care?
BInside the Earth
Activity 3: two kinds of wave.
The deepest hole ever drilled reached about 12 km. How do we know anything about the other 6,359?
Earthquakes send waves through the whole planet. How fast they travel, and whether they get through at all, depends on what they pass through.
This activity · about 40 minutes
- Run Model 5 with P and S waves, in solid rock and in liquid. Answer questions 1 to 4.
- Study the graph in Model 6 and answer questions 5 to 8.
A P wave is a “push” wave, and “P” stands for “primary” because P waves “arrive first at seismic stations” (Earle, 2019). S waves are shear waves, “which move particles perpendicular to their direction of propagation” (Earth Observatory of Singapore). In solid crustal rock, P waves travel at “between 3.0 km/s and 6.5 km/s”, and S waves at “between 1.5 km/s and 3.8 km/s” (Earle, 2019).
In Model 5, how does a particle move in an S wave? Directed
Switch to liquid. Which wave stops? Directed
Why can a liquid pass on a push but not a sideways shake? Think about what happens when you push water, and when you try to shear it sideways. Convergent
Squeeze a liquid and it pushes back, so a compression can pass from particle to particle. Shear a liquid and it just flows; nothing pulls the next particle back into place. “Liquids lack shear strength”, so “S-waves cannot propagate through liquids” (Earth Observatory of Singapore).
Write a rule that uses S waves to test whether a layer deep inside the Earth is solid or liquid. Convergent
If S waves pass through a layer, it is solid. If S waves are stopped by it, it is liquid.
Show the numbers as a table
Between which depths is the S-wave speed zero? Directed
Use your rule from question 4. What does the graph tell you about the layer between about 2,900 km and 5,150 km, and about the layer below it? Convergent
No S waves travel between about 2,900 and 5,150 km, so that layer is liquid: the outer core. Below 5,150 km S waves appear again, so the inner core is solid. The USGS: “The outer core is presumed to be liquid because it does not transmit shear (S) waves.”
At about 2,900 km the P-wave speed falls suddenly from about 13.7 to 8.1 km/s. What is the best explanation? Directed
Look at the top of the graph. In 1909 Andrija Mohorovičić noticed that stations some distance from an earthquake recorded two sets of waves, arriving a few seconds apart. Using the graph, suggest why. Divergent
Waves are faster below the crust, about 8 km/s in the mantle. Waves that dip into the mantle and come back up can overtake waves that stay in the slower crust, so two sets arrive. That showed a boundary between crust and mantle, now called the Mohorovičić discontinuity, or Moho (Earle, 2019).
BInside the Earth
Activity 4: the shadow zones.
Why do some seismometers on the far side of the world miss some of the waves from a large earthquake?
Seismometers all over the world record every large earthquake, but stations in a shadow zone miss some of its waves. The pattern of which stations receive which waves is a picture of the inside of the planet.
This activity · about 35 minutes
- Try the three Earth models in Model 7. Predict first, then look.
- Answer questions 1 to 6 as a team.
- Read how the core was discovered, then answer question 7.
In the first model the inside of the Earth is solid and the same all through. Which stations record S waves? Directed
The second model shows the main pattern recorded on the real Earth. Beyond about what angle from the earthquake do S waves stop arriving? Directed
Explain the S-wave shadow using your rule from Activity 3. Convergent
S waves heading to stations beyond about 103° would have to pass through the core. They do not arrive, so something in the core stops them. Only a liquid stops S waves, so the outer core is liquid. “The shadow zone results from S waves being stopped entirely by the liquid core” (IRIS).
P waves do travel through liquid, yet stations between about 104° and 140° receive no direct P waves. What must happen to P waves at the edge of the core? Convergent
They bend (refract) as they enter the core, because they suddenly slow down there (Model 6: from about 13.7 to 8.1 km/s). The bent waves come out farther round the Earth, beyond about 140°, leaving a band with no direct P waves: the P-wave shadow zone. The USGS describes “P waves being bent (refracted) by the liquid core” (USGS; IRIS).
Turn on the third model. Weak P waves now arrive inside the shadow zone. What causes them? Directed
A planet has seismometers and an S-wave shadow zone that starts at 60° from each earthquake, not 103°. What can you say about its core, compared with Earth’s? Divergent
The shadow starts closer to the earthquake, so S waves meet the liquid core along shorter paths. The liquid core must be larger, compared with the planet’s size, than Earth’s. (A team might also ask whether the waves travel in straight lines in that planet, which would change the answer.)
How the core was found
R. D. Oldham picked out P and S waves on seismograms, which allowed him “to detect a discontinuity” between core and mantle (Brush, 1980).
Beno Gutenberg “established the depth of this boundary as 2900 km” (Brush, 1980; the year is from NASA Goddard). The model used today puts it at 2,891 km (Dziewonski and Anderson, 1981).
“Not until 1926 did Harold Jeffreys refute the arguments for solidity and establish that the core is liquid” (Brush, 1980).
“In 1936 Inge Lehmann discovered the small inner core” (Brush, 1980), from weak P waves arriving in the shadow zone.
No one has ever seen the core. How sure should we be that the outer core is liquid? Give the evidence for your answer. Divergent
Very sure, though it is an inference. Several separate lines of evidence agree: the S-wave shadow from every large earthquake, the drop in P-wave speed at 2,891 km, and the P-wave shadow made by refraction. Scientists have checked it for a century with better instruments, and the model has kept working.
BInside the Earth
Activity 5: rocks from space.
Seismic waves show the core is liquid. How do we know it is made of iron?
Most meteorites are pieces of asteroids that formed with the rest of the solar system. Some are like the material Earth was built from; some are the cores of small worlds that broke apart.
This activity · about 35 minutes
- Study Model 8 and answer questions 1 to 3.
- Study Model 9 and answer questions 4 to 6.
- Put the argument for an iron core in order.
| Type | What it is made of | Where it came from | Australian example |
|---|---|---|---|
| Stony: chondrites | Mostly silicate minerals, with “tiny mineral spherules” called chondrules (Kansas Geological Survey) | “Chondrites are the material from which the solar system formed” (Natural History Museum) | Murchison, Victoria: fell in 1969; a “carbonaceous chondrite”, and “probably, the world’s most studied meteorite” (Museums Victoria) |
| Iron | “largely of iron-nickel alloys” (Kansas Geological Survey) | “Most iron meteorites are thought to be the cores of asteroids that melted early in their history” (Natural History Museum) | Mundrabilla, WA: its “12.4-ton main mass” is the largest meteorite found in Australia (WA Museum); a 2.5-tonne slice is in the South Australian Museum (Australian Museum) |
| Stony-iron | “both silicates and metals in approximately equal proportions” (Kansas Geological Survey) | Pallasites “are samples of the core-mantle boundary of an asteroid that melted” (UCLA Meteorite Museum) | Bendoc, Victoria: reported as a pallasite found in 1898, but since lost (Museums Victoria) |
“Of the witnessed meteorite falls on the earth, 94.5% are stones” (Kansas Geological Survey).
An iron fall in the Northern Territory: at Henbury, 145 km south-west of Alice Springs, a fall about 4,700 years ago left 12 craters, the largest “180m wide and 15m deep” (NT Parks). The fragments are iron meteorites that “consist of 90% iron and 8% nickel” (Museums Victoria). The Arrernte name for the crater area is Tatyeye Kepmwere (Parks and Wildlife Commission of the Northern Territory, 2002).
Which kind of meteorite best shows the raw material the whole Earth formed from? Directed
An asteroid melts, then cools. Iron meteorites are its core; some stony meteorites are its outer rock. What happened to the iron while the asteroid was molten? Convergent
The denser iron sank to the centre and the lighter rock stayed outside, so the asteroid separated into a metal core and a rocky outer part. When it later broke up, the pieces became “stony meteorites from fragmented mantle rock, and iron meteorites from fragmented core” (Panchuk, 2019).
Mundrabilla was found on the Nullarbor Plain. Suggest why so many meteorites are found on the Nullarbor and in other deserts. Divergent
A dark rock is easy to see on flat, pale, bare ground with few plants, and a dry climate means meteorites rust away slowly. (This is a reasonable inference; the lesson’s sources do not discuss it.)
Show the numbers as a table
The whole Earth’s average density is about 5.5 g/cm³. Continental rock is about 2.7. What must be true of the inside? Directed
Compare the density of the core with the densities of rock and of iron meteorites. What does the comparison suggest the core is made of? Convergent
The core’s density (about 10 to 13 g/cm³) is far above any rock, and close to iron under very high pressure. Together with iron-nickel meteorites such as Henbury’s, that points to a core of mostly iron with some nickel. The USGS adds that the core is “presumed to be composed principally of iron, with about 10 percent alloy of oxygen or sulfur or nickel”.
An iron meteorite is not a piece of Earth’s core. Why is it still useful evidence? What is its weakness as evidence? Divergent
Useful: it shows that small bodies made of the same starting material melted and formed iron-nickel cores, so Earth, which melted too, probably did the same. Weakness: it is an analogy, not a sample. The Natural History Museum treats iron meteorites as a guide to how planetary cores formed, not as pieces of Earth’s core. The seismic and density evidence has to agree before the conclusion is strong.
Put the argument in order
BInside the Earth
Activity 6: the layers, to scale.
If the Earth were a peach, how thick would the skin be?
Put the evidence together and you get the layers: a thin rocky crust, a thick solid mantle that flows very slowly, a liquid outer core and a solid inner core.
This activity · about 40 minutes
- Open each layer in Model 10. Answer questions 1 to 4.
- Compare the two kinds of crust in Model 11 and answer questions 5 to 7.
- Sort the statements about the crust.
Which layer is liquid? Directed
The inner core is hotter than the outer core, yet it is solid. Explain why. Convergent
Pressure keeps rising towards the centre. “The inner core is solid because the pressure at that depth is so high that it keeps the core from melting” (Panchuk, 2019). High pressure raises the temperature at which iron melts.
Continental crust averages about 35 km thick. What fraction of the Earth’s radius (6,371 km) is that? Directed
The crust and the top of the mantle together make the rigid lithosphere, about 100 km thick, over a weak asthenosphere. Why do geologists need both ways of dividing the layers, by composition and by how they behave? Divergent
Composition (crust, mantle, core) tells you what the rock is made of. Behaviour (rigid lithosphere, weak asthenosphere) tells you how it moves. Plates are pieces of lithosphere, so they include the top of the mantle as well as the crust. Earle (2019): “the upper approximately 100 km of the Earth is known as the lithosphere”, and “The next 150 km is the asthenosphere”.
| Continental crust | Oceanic crust | |
|---|---|---|
| Thickness | Average about 35 km (Britannica); 60 to 80 km under major mountain ranges (Panchuk, 2019) | 5 to 10 km (Earle, 2019) |
| Density | About 2.7 g/cm³ | About 3.0 g/cm³ (Lumen Learning) |
| Rock | “predominantly granitic rock” (Britannica); “predominantly felsic” (Panchuk, 2019) | “predominantly mafic” (Panchuk, 2019): basalt and gabbro |
| Oldest | Rocks about 4 billion years old (Britannica); zircon grains from the Jack Hills, WA, 4,404 ± 8 million years old (Wilde and others, 2001) | In the main ocean basins, “everywhere less than about 180 million years old” (NOAA) |
Which kind of crust is denser? Directed
Continental rocks are up to about 4 billion years old, but ocean floor in the main basins is less than about 180 million years old. Suggest what happens to old ocean floor. Convergent
It is destroyed: dense oceanic crust sinks back into the mantle at subduction zones, while new ocean floor forms at mid-ocean ridges. Light continental crust does not sink, so it survives for billions of years. Earle (2019) explains that older sea floor has been subducted. Activity 8 looks at why.
Back to the peach. If the Earth were a peach 7 cm across, about how thick would the continental crust be? Show your working. Divergent
Radius 3.5 cm. 0.5% of 3.5 cm is about 0.02 cm, or 0.2 mm: about as thin as a peach’s skin. (35 ÷ 6,371 × 35 mm ≈ 0.19 mm.)
Apply it: continental or oceanic?
CHeat and movement
Activity 7: where the heat comes from.
Why is rock 4.4 km under the Cooper Basin hot enough to boil water, and where does that heat come from?
The Earth is hot inside, and the heat drives volcanoes, earthquakes and the movement of plates. About half of it comes from atoms decaying inside the rocks themselves.
This activity · about 40 minutes
- Study the graph in Model 12 and answer questions 1 to 4.
- Read Model 13 and answer questions 5 to 8.
- Put the energy chain in order, from a uranium atom to a hot spring.
Show the numbers as a table
The geothermal gradient is “the rate at which Earth’s temperature increases with depth” (Britannica). Heat moves by conduction, “heat transfer by collisions between molecules”, and by convection, which “carries heat to the surface of the mantle much faster than heating by conduction” (Panchuk, 2019).
From the graph, about how hot is the base of the mantle, at about 2,890 km? Directed
Where is the gradient steepest, with temperature climbing fastest for each kilometre down? Directed
Explain the shape of the graph: steep in the lithosphere, then much flatter through the mantle. Use the words conduction and convection. Convergent
The rigid lithosphere can pass heat upward only by conduction, which is slow, so a large temperature difference builds up across it. The mantle below is solid but flows slowly, so it carries heat up by convection, which is much faster; only a small temperature difference is needed. Earle (2019): the smaller gradient in the mantle “has been interpreted to indicate that the mantle is convecting”.
The mantle is at 1,400 to 3,800 °C, hot enough to melt rock at the surface, yet it is almost entirely solid. Suggest why. Divergent
Pressure rises with depth, and high pressure raises the temperature at which rock melts, as in the inner core (Activity 6). Only between about 100 and 250 km does the temperature come “very close to the melting boundary for dry mantle rock” (Earle, 2019), which is why the asthenosphere is weak.
“The current total heat flux from the Earth to space is 44.2±1.0 TW” (KamLAND Collaboration, 2011); another estimate is “47±2 TW” (Davies and Davies, 2010). By measuring particles called geoneutrinos, KamLAND found that “decay of uranium-238 and thorium-232 together contribute 20.0” TW, and that “heat from radioactive decay contributes about half of Earth’s total heat flux”. The rest is heat left over from the Earth’s formation: “Earth’s primordial heat supply has not yet been exhausted”.
The main heat-producing isotopes are uranium-235, uranium-238, potassium-40 and thorium-232 (Earle, 2019). “As they decay, the fast-moving particles they release smash into their surroundings, dumping their energy as heat” (BBC Science Focus). “Radioactive decay produced more heat early in Earth’s history than it does today” (Panchuk, 2019).
The Habanero 1 well was drilled to extract hot water from granite buried under the Cooper Basin. It “was completed at 4,421 m”, and “The static rock temperature at the bottom of the well is about 250°C” (Wyborn and others, 2005). A pilot power plant ran for five months in 2013 (Geoscience Australia).
A belt of South Australia has “anomalously high surface heat flow (92 ± 10 mW m-2)”, against about 54 in the western Gawler Craton. The cause is “exceptional surface heat production values, mainly hosted in Palaeoproterozoic to Mesoproterozoic granites”, with “an unusual enrichment in U and Th” (Neumann and others, 2000).
Work out the average geothermal gradient in the Habanero well. Assume the ground surface is about 25 °C. Show your working. Directed
(250 − 25) °C ÷ 4.421 km ≈ 225 ÷ 4.4 ≈ 51 °C per km. That is well above, 1.5 to 2 times, the 25 to 35 °C per km that Britannica gives for stable continental interiors.
Use Model 13 to explain why the Habanero gradient is so much steeper than usual. Convergent
The granites under parts of South Australia are unusually rich in uranium and thorium. As these decay, their particles heat the surrounding rock, so the crust itself makes extra heat. Geoscience Australia describes basement rocks in Australia, “especially granites, with unusually high heat-generating properties”.
Roughly what share of the heat flowing out of the Earth comes from radioactive decay? Directed
A student says, “The ground is warm because heat comes straight up from the core.” Use the evidence in Model 13 to improve that statement. Divergent
Some heat does come from deep inside, carried up by convection in the mantle and then conducted through the lithosphere. But about half of the Earth’s heat is made by radioactive decay in the rocks themselves, much of it in the mantle and some in the crust. In South Australia, granites rich in uranium and thorium heat the crust from within, which is why heat flow there is high.
Put the energy chain in order
CHeat and movement
Activity 8: plumes and plates.
Hawaii is thousands of kilometres from a plate boundary. Why is it volcanic, and what do its islands tell us about the plate under them?
Heat inside the Earth makes the mantle flow, lifts plumes of hot rock, and sets the plates moving. A chain of islands can record how fast.
This activity · about 40 minutes
- Pick volcanoes in Model 14 and answer questions 1 to 5.
- Step through Model 15 and answer questions 6 to 10.
- Sort the statements by the process they describe.
The Hawaiian Islands “have formed in the middle of the Pacific Ocean more than 3,200 km from the nearest plate boundary”. J. Tuzo Wilson suggested they formed as the “Pacific Plate moving over a deep, stationary hotspot in the mantle” (USGS). Hot spots are “localized sources of high heat energy (thermal plumes)” (USGS).
What pattern do the ages show? Directed
Explain the pattern. What stays still, and what moves? Convergent
The plume of hot rock rising from deep in the mantle stays roughly still, and the Pacific Plate moves over it. Each volcano forms over the hot spot and is then carried away, so the farther a volcano is from the hot spot, the longer ago it formed. The USGS notes that some newer studies suggest hot spots are not completely fixed.
Choose Kauai and Midway in Model 14. What speeds do they give? Compare them with the USGS figure for the Pacific Plate along the chain, “approximately 10 centimeters per year”. Directed
Kauai: 519 km ÷ 5.1 million years ≈ 10.2 cm per year. Midway: 2,432 km ÷ 27.7 million years ≈ 8.8 cm per year. Both are close to the USGS figure of about 10 cm per year. (A shortcut: kilometres per million years is the same as millimetres per year.)
Maui gives about 17 cm per year, much faster than the others. Suggest why a young island close to the hot spot gives an unreliable speed. Convergent
The hot spot is wide (some scientists estimate “about 200 miles across”, USGS), so volcanoes do not all start at one point, and a small error in a short distance or a young age makes a big difference to the speed. Older, more distant volcanoes average out these errors, so they give a better speed.
Eastern Australia has a 2,000 km chain of extinct volcanoes, from the Whitsundays to near Melbourne, formed “as Australia moved northwards over a hotspot” (ANU). It records “volcanic activity between 33 and 9 million years ago” (Davies and others, 2015). Work out the speed and compare it with Geoscience Australia’s figure: the plate “travels around seven centimetres each year”. Some sections of the track have no volcanoes, where the lithosphere is thick. Suggest why. Divergent
The volcanoes span 33 − 9 = 24 million years. 2,000 km ÷ 24 million years ≈ 83 km per million years ≈ 8 cm per year, close to Geoscience Australia’s 7 cm per year. Volcanoes formed only where the lithosphere is “thinner than 130 kilometres” (ANU): where it is thicker, the rising plume cannot get close enough to the surface to melt, so the plate passed over the hot spot without erupting.
At step 2, why does new oceanic plate move away from the ridge? Use the shape of the sea floor in the model. Convergent
Rock under the ridge is hot and expanded, so the ridge stands high. As the plate moves away it cools, contracts and sinks lower. Gravity makes the plate slide down the slope away from the ridge: ridge push, “the push of oceanic lithosphere down from a ridge area” (Earle, 2019). Hot mantle rises to fill the gap and partly melts, making new crust.
At step 3, why does the oceanic plate sink under the continent and not the other way round? Convergent
Oceanic crust is denser, about 3.0 g/cm³ against about 2.7 for continental crust (Model 11), and old oceanic plate has cooled, making it denser still: “Often it is the older and colder plate that is denser and subducts” (Earle, 2019). Continental material “will not be subducted because it is too light” (Earle, 2019).
Which force did Forsyth and Uyeda (1975) find controls how fast oceanic plates move? Directed
Earle (2019) notes that “plates that are attached to subducting slabs (e.g., Pacific, Australian, and Nazca Plates) move the fastest”. Explain how this is evidence for slab pull. Convergent
If slab pull drives plates, then plates with a long slab sinking at their edge should be pulled hardest and move fastest, and plates with no slab should move slowly. That is what is observed, so the observation supports slab pull as the main force.
Draw the whole system together. Starting from heat inside the Earth, explain in a few sentences how energy ends up moving the Australian Plate north-east at about 7 cm per year. Divergent
Heat from radioactive decay and from the Earth’s formation warms the mantle. Hot, less dense rock rises and cooler, denser rock sinks, so the solid mantle convects slowly. At mid-ocean ridges rising hot rock lifts the sea floor and makes new crust, and the plate slides away (ridge push). As it ages it cools and becomes denser until, at a subduction zone, it sinks back into the mantle and pulls the rest of the plate behind it (slab pull). The Australian Plate is attached to sinking slabs along its northern edge, which helps explain why it is one of the fastest-moving plates.
Apply it: which process?
Team reflection
5Show what you know
Show what you know.
Nine questions, one for each of the I can statements on screen 1. You get one try at each, so think before you tap.
A sandstone has symmetrical ripple marks. What does uniformitarianism let a geologist infer?
Which is the best example of a limitation of uniformitarianism?
How do S waves show that the outer core is liquid?
Why is there a P-wave shadow zone between about 104° and 140° from an earthquake?
How do iron meteorites support the idea that the Earth’s core is mostly iron?
Which statement about the layers is correct?
Why is heat flow unusually high across part of South Australia?
Why do the Hawaiian volcanoes get older towards the north-west?
Which best explains why an oceanic plate sinks under a continent, and what this does to the plate?
Team record
Three pages: team roles and a reflection for each activity, the key convergent questions with space for the team’s answers, a blank cross-section to label the layers, and tables for the Habanero gradient and the Hawaiian speeds.
For teachers
Curriculum
SACE Board of South Australia, Stage 1 Earth and Environmental Science Subject Outline (reissued for 2025), Topic 3: Processes in the Geosphere. NT students take the subject as part of the NTCET. The outline’s list of topics writes “Processes in the geosphere”; the lesson uses the topic’s own heading, “Processes in the Geosphere”. The topic outline begins:
In this topic students explore how some of the Earth’s most spectacular events are due to energy transformations in the geosphere. They analyse how energy from the Earth’s interior drives movements of tectonic plates in the geosphere, which causes volcanic and earthquake activity.
Students investigate evidence that provides information about the structure of the Earth, and learn how scientists analyse this evidence to develop models that describe changes to the Earth’s structure. Students use the principle of uniformitarianism to develop their creative thinking by making reasonable predictions based on evidence.
The topic’s Science Understanding statements and dot points, all of which this lesson covers:
Observation of present-day processes can be used to infer past events and processes, by applying the principle of uniformitarianism.
- Explain how features of sedimentary rocks can provide information about their history.
The study of seismic waves and meteorites provides evidence for the layered structure of the Earth.
- Explain how the presence of shadow zones provides information about the layered structure of the Earth.
- Explain how the composition of a meteorite can provide evidence of the internal composition, of the Earth.
- Describe the structure, relative thickness, composition and state of each layer of the Earth’s interior.
- Describe how continental crust is different from oceanic crust.
Some processes within and between Earth systems require energy that originates from the interior of the Earth.
- Interpret graphs of the Earth’s geothermal gradient.
- Describe the transfer of geothermal energy from the decay of naturally occurring radioactive elements to rocks.
Transfers and transformations of energy in the Earth’s interior cause plume formation and drive the movement of tectonic plates, through processes such as mantle convection, slab pull, and ridge push.
- Describe how plumes from the mantle can transfer heat energy from the Earth’s interior to produce ‘hot-spot’ volcanic activity and form an island chain.
- Explain why new crust is pushed away from mid-ocean ridges.
- Explain why an oceanic plate is subducted in collisions with a continental plate.
Where the lesson covers them:
- How features of sedimentary rocks provide information about their history, by uniformitarianism: Activity 1 (Model 1, Hallett Cove, Nilpena, way-up features, the environment sort), Activity 2 (limits; Pluto and Mars), x1 and x2.
- How shadow zones show the layered structure: Activity 3 (P and S waves, the speed graph), Activity 4 (the shadow-zone model and the history of the core), x3 and x4.
- How meteorites are evidence of the Earth’s internal composition: Activity 5 (meteorite types and Australian examples, including Henbury in the Northern Territory; density; the argument chain), x5.
- The structure, relative thickness, composition and state of each layer, and continental against oceanic crust: Activity 6 (the scaled cut-away, Model 11, the crust sort), x6.
- Graphs of the geothermal gradient, and heat from radioactive decay: Activity 7 (the temperature graph, the heat budget, Habanero, the South Australian heat flow anomaly, the energy chain), x7.
- Plumes, hot spots and island chains; mantle convection, slab pull and ridge push; why new crust moves away from ridges and why oceanic plates are subducted: Activity 8 (the Hawaiian chain, the eastern Australian hot-spot track, the ridge-to-trench model, the process sort), x8 and x9.
The lesson uses these of the outline’s possible contexts: interpreting the surface of Pluto by uniformitarianism; volcanic landforms in south-east South Australia (Mount Gambier, Activity 1); limitations of uniformitarianism; discussing how radioactive decay produces heat; the ages of the Hawaiian Islands and plate movement; and modelling hot-spot volcanism. In place of the outline’s clay-ball model of the crust, Activity 6 uses a scaled cut-away. The history of the core (Oldham, Gutenberg, Jeffreys, Lehmann) adapts the context on contributions from different scientists, which the outline sets for plate tectonics.
Stage 1 is assessed through an investigations folio and skills and applications tasks. The hot-spot speed calculation and the Habanero gradient suit a skills and applications task; Activity 1 can lead into a field investigation of sedimentary features at Hallett Cove or a local cutting.
How the lesson is taught
The lesson uses POGIL, Process Oriented Guided Inquiry Learning. The POGIL Project describes it as “a student-centered, group-learning instructional strategy and philosophy”, in which students “work in small teams with the instructor acting as a facilitator”. Each activity gives students a model (data, a table, a diagram or a simulation) “followed by guiding questions designed to lead them toward formulation of their own valid conclusions” (POGIL Project). The questions follow a learning cycle of exploration, concept invention and application, and come in three kinds, labelled on each question: directed, where the answer is “found directly in the model”; convergent, which “requires analysis and synthesis”; and divergent, where students go further by “pondering, further exploring, and generalizing” (University of Texas at Arlington workshop handout). Teams of three or four take the roles of manager, recorder, presenter and reflector (POGIL Project). Each activity ends with an application: a sort, a chain or a calculation.
The evidence for POGIL is positive but modest on test scores. A meta-analysis of 21 studies with 7,876 students found a small effect on achievement (Hedges’ g = 0.29) and that POGIL roughly doubled the odds of passing a course (odds ratio 2.02) (Walker and Warfa, 2017). Only two of those studies were in high schools, and most lacked checks on how faithfully POGIL was carried out, so differences in how it was run may explain much of the variation between studies. An Australian study of first-year chemistry at Curtin University found gains in students’ self-efficacy (d = 0.42 and 0.69 across two semesters) but did not measure achievement (Vishnumolakala and others, 2017). We found no study of POGIL in geoscience. The obstacles teachers report are preparation time, a shortage of activities and pressure to cover content (Hu and others, 2016).
- Timing. About seven hours: eight 50-minute lessons, one activity per lesson. Use the start of lesson 1 for screen 1 and the end of lesson 8 for screen 10. Each activity leaves about 10 minutes for teams to report.
- Running it. Put students in teams of three or four on one device, with the recorder typing. Rotate roles each activity. Stop the class after key questions (Activity 1, question 4; Activity 3, question 4; Activity 4, question 3; Activity 8, question 10) and have presenters share; the model answers are for teams to check against afterwards, not a replacement for that discussion.
- The model answers. A model answer opens only after the team has typed something. Students working alone can use the lesson as guided reading, but the roles assume a team.
- Facilitating. Answer questions with questions (“What does Model 6 show at 2,900 km?”) and visit teams that go quiet. The reflector’s note at the end of Activity 8 gives the team something to report on how it worked.
- Saved work. Answers save in the browser on the device being used. A team that changes devices should keep the printable team record.
Handle with care
- The last eruption of Mount Gambier “is actually thought to have been witnessed by Aboriginal people” (Science Network WA). If you add a field trip there, consider local knowledge as well as the geology. The lesson does not tell an Aboriginal story about the eruptions, because we did not have a source that the Traditional Owners have approved for sharing.
- Wolfe Creek crater is known to the Djaru people as Kandimalal. It is mentioned only in the notes and references.
- Henbury: the crater area holds a recorded sacred site, and the 2002 draft plan of management says the area’s stories will be used for interpretation only “after agreement by the Aboriginal custodians of the site”. The lesson gives the Arrernte name and nothing more. A 1934 newspaper account describes a “fire-devil”; Hamacher and Goldsmith (2013) identify its words as Luritja and caution against interpreting its translation without context.
- Groups need managing. Watch for one student doing the work while others watch; rotating roles and asking the reflector to report help.
Misconceptions the activities target
- The mantle, or the asthenosphere, is liquid magma (Activity 6, question 1; x6). It is almost entirely solid and flows very slowly; only the outer core is liquid. This and the next item, and the crust and lithosphere item, appear in the NAGT list of common Earth science misconceptions.
- Magma comes from a molten layer under the crust, or from the core (Activity 6, question 1).
- Convection only happens in liquids (Activity 7, question 3; Activity 8, Model 15). The NAGT list notes this under the asthenosphere item.
- Crust and lithosphere mean the same thing (Activity 6, question 4).
- Uniformitarianism means everything happens slowly (Activity 2, questions 1 to 3; x2).
- The ground is warm because heat comes straight from the core (Activity 7, question 8; x7).
- The hot spot moves under a still plate (Activity 8, question 2; x8).
- The crust is a thick layer (Activity 6, questions 3 and 7). King (2000), cited by Pickard and others (2011), found that “nearly half the teachers asked had no real concept of the scale of the crust relative to the whole Earth”.
About the data and the models
- The wave model (Activity 3) exaggerates particle movement and shows a plane wave; real waves spread out from the earthquake.
- The speed graph (Activity 3) uses the Preliminary Reference Earth Model (Dziewonski and Anderson, 1981) as tabulated by Shearer, without the model’s 3 km ocean layer. The model’s Moho is at a global-average depth of 24.4 km.
- The shadow-zone model (Activity 4) shows which stations receive waves, not the curved paths of the waves. Stations are every 10°.
- The density chart (Activity 5) uses Lumen Learning for the crust, the Preliminary Reference Earth Model for the mantle and core, and NASA for the whole-Earth average.
- The cut-away (Activity 6) is drawn to scale from the Preliminary Reference Earth Model, with the crust drawn 35 km thick.
- The temperature graph (Activity 7) uses the table in Earle (2019), Figure 9.2.1. Temperatures deep inside the Earth are estimates; see below.
- The Hawaiian ages (Activity 8) come from NOAA Ocean Exploration’s data table, which does not name its source.
- The ridge-to-trench model (Activity 8) is schematic, not to scale.
- Quotations in the screens are short excerpts checked against the source pages.
Where sources disagree
- Shadow zones: S waves absent beyond 103° (Earle, 2019; IRIS); P waves absent from 104° to 140° (IRIS; USGS) or from 103° to 150° (Earle, 2019). Many textbooks give 103° to 142° or 143°; we did not find those figures in the sources we checked.
- The core-mantle boundary: 2,900 km (Gutenberg, via Brush, 1980), 2,890 km (Earle, 2019) or 2,891 km (Preliminary Reference Earth Model). Gutenberg’s work is dated 1913 by NASA Goddard; many textbooks give 1914.
- The inner core boundary: 5,100 km (Earle’s table) or 5,149.5 km (Preliminary Reference Earth Model).
- Continental crust: an average of 30 km (USGS), 35 km (Britannica) or 30 to 50 km (Panchuk, 2019). Oceanic crust: about 5 km (USGS) or 5 to 10 km (Earle, 2019).
- Oldest oceanic crust: about 180 million years in the main ocean basins (NOAA), but about 280 million years in the eastern Mediterranean (Earle, 2019).
- Temperatures: Earle’s text gives about 3,500 °C at the base of the mantle and 5,000 °C at the centre, while his own table gives 3,800 °C and 5,100 °C. Panchuk (2019) gives the centre as more than 6,000 °C, and Anzellini and others (2013) about 5,500 K (about 5,200 °C) at the inner core boundary.
- Near-surface geothermal gradient: 15 to 30 °C per km in the upper 100 km (Earle, 2019) or 25 to 35 °C per km in stable continental interiors (Britannica).
- The Earth’s total heat flow: 44.2 TW (KamLAND Collaboration, 2011) or 47 TW (Davies and Davies, 2010).
- Hawaiian ages: single ages from NOAA (for example Kauai 5.1 and Oahu 3.7 million years) against ranges from the USGS (Kauai 5.6 to 3.8, Oahu 3.4 to 2.2). The bend in the Hawaiian-Emperor chain is dated about 43 million years (USGS) or about 50 million years (Stock, 2006).
- Hot spots: the USGS notes that newer studies suggest hot spots are “neither deep phenomena nor ‘fixed’ in position over geologic time”, while the outline and Davies and others (2015) treat plumes as deep.
- What drives plates: Forsyth and Uyeda (1975) and the USGS put slab pull first. The same USGS page also says “the plate-driving force is the slow movement of hot, softened mantle”, and Earle (2019) gives convection an important role.
- The mantle: “almost entirely solid” (Panchuk, 2019) against “semi-solid” and “partially molten” (USGS). The USGS wording can feed the liquid-mantle misconception.
- Mount Gambier’s last eruption: 4,000 to 4,300 years ago (South Australian heritage fact sheet) or over 5,000 years ago (University of Melbourne), or about 5,000 (The Conversation).
- Henbury: 4,700 years ago (NT Parks), “not more than 4700 years” before the present (Parks and Wildlife Commission of the Northern Territory, 2002), or 4,200 ± 1,900 years from carbon-14 in the meteorites (Shoemaker and others, 2005); 12 craters (NT Parks) or 13 to 14 (Hamacher and Goldsmith, 2013).
- “The present is the key to the past”: usually credited to Archibald Geikie, but we found no source quoting him using it.
Answers at a glance
- Activity 1: q1 lopsided ripples; q2 no, it dried in the air; q6 shallow water over sand. Sort: lopsided ripples, cross-beds and rounded pebbles, river or current; symmetrical ripples, waves; mud cracks and salt, drying; graded bed, underwater flow; jumbled boulders on scratched rock, glacier.
- Activity 2: q1 they assumed change is always slow. Sort: ripples, mud cracks and Mars pebbles are safe; the Scabland, banded iron and the river before plants need care.
- Activity 3: q1 side to side; q2 the S wave; q5 about 2,900 to 5,150 km; q7 solid rock into liquid.
- Activity 4: q1 all of them; q2 about 103°; q5 P waves bent or reflected by the inner core.
- Activity 5: q1 chondrites; q4 much denser. Argument chain: chondrites, crust short of iron, iron meteorites, density, seismic waves, conclusion.
- Activity 6: q1 the outer core; q3 about 0.5%; q5 oceanic. Sort: granitic, 2.7, thick under mountains and 4-billion-year-old rocks are continental; basalt, 3.0, 5 to 10 km and subducted are oceanic. Peach: about 0.2 mm.
- Activity 7: q1 about 3,800 °C; q2 the top 100 km; q5 about 51 °C per km; q7 about half. Energy chain: decay, particles, collisions, rock warms, conduction, hot spring.
- Activity 8: q1 farther is older; q3 Kauai about 10.2 and Midway about 8.8 cm per year; q5 about 8 cm per year; q8 slab pull. Sort: sinking plate, ten times stronger, slab pull; sliding from the ridge, hot young sea floor, ridge push; mid-plate volcano, age chain, plume.
- Exit check: x1 waves in shallow water; x2 the enormous floods; x3 S waves cannot cross liquid; x4 P waves bend at the core; x5 cores of melted bodies; x6 solid mantle, liquid outer core; x7 uranium and thorium in granites; x8 the plate moves over the plume; x9 cold, dense plate sinks and pulls.
Saved progress
Answers, team role and notes are saved only in this browser on this device. Nothing is sent anywhere.
References
- Anzellini, S., Dewaele, A., Mezouar, M., Loubeyre, P., & Morard, G. (2013). Melting of iron at Earth’s inner core boundary based on fast X-ray diffraction. Science, 340, 464–466. https://doi.org/10.1126/science.1233514
- APS News (2023, August). Article on Inge Lehmann and her 1936 paper on the inner core.
- Australian Museum (n.d.). Mundrabilla iron meteorite.
- Britannica (n.d.). Uniformitarianism; Sedimentary rock: evaporites; Glacial landform: glacial deposition; Lake Eyre; Continental crust; Geothermal gradient.
- Brooklyn Botanic Garden (n.d.). Great moments in plant evolution: plants invade the land.
- Brush, S. G. (1980). Discovery of the Earth’s core. American Journal of Physics, 48, 705.
- Darwin Online (n.d.). Chancellor, G. Introduction to Lyell’s Principles of Geology.
- Davies, D. R., Rawlinson, N., Iaffaldano, G., & Campbell, I. H. (2015). Lithospheric controls on magma composition along Earth’s longest continental hotspot track. Nature, 525, 511–514. https://doi.org/10.1038/nature14903 (reported by ANU via Phys.org, 2015)
- Davies, J. H., & Davies, D. R. (2010). Earth’s surface heat flux. Solid Earth, 1, 5–24. https://doi.org/10.5194/se-1-5-2010
- Dziewonski, A. M., & Anderson, D. L. (1981). Preliminary reference Earth model. Physics of the Earth and Planetary Interiors, 25, 297–356 (values as tabulated in Shearer, P. M., Introduction to Seismology, 2nd ed., appendices).
- Earle, S. (2019). Physical Geology (2nd ed.), 6.4, 8.4, 9.1, 9.2, 10.4, 10.5 and 18.2. BCcampus. CC BY 4.0.
- Earth Observatory of Singapore (n.d.). Why can’t S-waves travel through liquids?
- Forsyth, D., & Uyeda, S. (1975). On the relative importance of the driving forces of plate motion. Geophysical Journal of the Royal Astronomical Society, 43(1), 163–200. https://doi.org/10.1111/j.1365-246X.1975.tb00631.x
- Geoscience Australia (2017). Australia officially moves 1.8 metres northeast; (2024) Australia’s Energy Commodity Resources: Geothermal.
- Hamacher, D. W., & Goldsmith, J. (2013). Aboriginal oral traditions of Australian impact craters. Journal of Astronomical History and Heritage, 16, 295–311.
- Hu, H. H., Kussmaul, C., Knaeble, B., Mayfield, C., & Yadav, A. (2016). Results from a survey of faculty adoption of Process Oriented Guided Inquiry Learning (POGIL) in computer science. ITiCSE ’16, 186–191. https://doi.org/10.1145/2899415.2899471
- IRIS / EarthScope (n.d.). Seismic shadow zone: basic introduction; Seismic shadow zones: S wave shadow zone (animations).
- IUGS Geoheritage (n.d.). Dry Falls and the Channeled Scabland.
- KamLAND Collaboration: Gando, A., and others (2011). Partial radiogenic heat model for Earth revealed by geoneutrino measurements. Nature Geoscience, 4, 647–651. https://doi.org/10.1038/ngeo1205
- Kansas Geological Survey: Suchy, D. (2011). Meteorites in Kansas (Public Information Circular 26).
- Lumen Learning (n.d.). Characteristics of the crust. Geology (CK-12, CC BY-NC).
- Matthews, R. (2010, 11 March). What makes the rock inside volcanoes so hot? BBC Science Focus.
- Museums Victoria (n.d.). Eleven incredible meteorites; The Murchison meteorite; collections article on the Henbury meteorites (16412).
- NASA (2015, 24 July). New Horizons discovers flowing ices on Pluto; NASA Scientific Visualization Studio (2016). Pluto’s heart: a cosmic “lava lamp”; NASA Earth Fact Sheet.
- NASA Astrobiology (n.d.). The biology behind banded iron formations.
- NASA Goddard Space Flight Center (n.d.). History of the detection of the core (mirror of the Royal Observatory of Belgium page).
- NASA JPL (2013, 30 May). Pebbly rocks testify to old streambed on Mars.
- National Parks and Wildlife Service SA (n.d.). Hallett Cove Conservation Park; The Nilpena story.
- Natural History Museum (n.d.). Types of meteorites.
- Neumann, N., Sandiford, M., & Foden, J. (2000). Regional geochemistry and continental heat flow: implications for the origin of the South Australian heat flow anomaly. Earth and Planetary Science Letters, 183, 107–120. https://doi.org/10.1016/S0012-821X(00)00268-5
- Newfoundland and Labrador Department of Energy and Mines (n.d.). Sedimentary structures.
- NOAA (1996). Oldest ocean crust (news release); NOAA Ocean Exploration (n.d.). Hawaiian map data table.
- NT Parks (n.d.). Henbury Meteorites Conservation Reserve. Northern Territory Government.
- Panchuk, K. (2019). Physical Geology (First University of Saskatchewan Edition), chapter 3 (bookdown edition by D. Dunnington), 8.4 and 9.5 (via LibreTexts and BCcampus).
- Parks and Wildlife Commission of the Northern Territory (2002). Henbury Meteorites Conservation Reserve: draft plan of management.
- Pickard, M., Licona, P., & Guertin, L. (2011). Abstract, paper 196122, Geological Society of America Annual Meeting, on students’ and teachers’ ideas about Earth’s layers.
- POGIL Project (n.d.). What is POGIL?; Using POGIL materials (team roles).
- Preiss, W. V. (2019). New Hallett Cove geological map. MESA Journal, 91. Geological Survey of South Australia.
- Romano, M. (2015). Reviewing the term uniformitarianism in modern Earth sciences. Earth-Science Reviews.
- Science Network WA, via Phys.org (2014, 31 July). Australian volcanoes a case for dating technique.
- Shoemaker, E. M., Macdonald, F. A., & Shoemaker, C. S. (2005). Geology of five small Australian impact craters. Australian Journal of Earth Sciences, 52, 529–544.
- South Australian Department for Environment and Water (n.d.). Mount Gambier Volcanic Complex State Heritage Area (fact sheet).
- Stock, J. M. (2006). The Hawaiian-Emperor bend: older than expected. Science, 313, 1250–1251. https://doi.org/10.1126/science.1131789
- The Conversation (2016). Australia’s volcanic history is a lot more recent than you think.
- UCLA Meteorite Museum (n.d.). Highlights.
- University of Melbourne, via EurekAlert (2011, 5 July). Joyce, B., on Victoria’s and South Australia’s volcanoes.
- University of Texas at Arlington College of Science (n.d.). POGIL workshop handout.
- USGS (n.d.). This Dynamic Earth: Inside the Earth, Hotspots, Developing the theory, Some unanswered questions; The Interior of the Earth (Robertson); shadowzone.gif; Volcano Watch: Island of Hawai‘i sits at the end of a long, old chain of 125 volcanoes; Volcanoes of Hawaii.
- Vishnumolakala, V. R., Southam, D. C., Treagust, D. F., Mocerino, M., & Qureshi, S. (2017). Students’ attitudes, self-efficacy and experiences in a modified process-oriented guided inquiry learning undergraduate chemistry classroom. Chemistry Education Research and Practice, 18, 340–352. https://doi.org/10.1039/C6RP00233A
- WA Museum (n.d.). Mundrabilla meteorite.
- Walker, L., & Warfa, A.-R. M. (2017). Process oriented guided inquiry learning (POGIL®) marginally effects student achievement measures but substantially increases the odds of passing a course. PLoS ONE, 12(10), e0186203. https://doi.org/10.1371/journal.pone.0186203
- Wilde, S. A., Valley, J. W., Peck, W. H., & Graham, C. M. (2001). Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago. Nature, 409, 175–178. https://doi.org/10.1038/35051550
- Wyborn, D., de Graaf, L., Hann, S., & Nicholson, B. (2005). Progress in geothermal energy development, Cooper Basin, South Australia. The APPEA Journal, 45(1), 175–184. https://doi.org/10.1071/AJ04015
Sources by screen
- Screen 2: Earle (2019) 6.4; Panchuk (2019) 8.4; Panchuk (2019) 9.5; Britannica: uniformitarianism; Britannica: evaporites; Britannica: glacial deposition; Newfoundland and Labrador; Parks SA: Hallett Cove; Preiss (2019); Parks SA: Nilpena; Mount Gambier fact sheet; University of Melbourne (2011)
- Screen 3: IUGS: Channeled Scabland; NASA Astrobiology; Romano (2015); Brooklyn Botanic Garden; Darwin Online; NASA: Pluto ices; NASA SVS: Pluto; NASA JPL: Mars streambed
- Screen 4: Earle (2019) 9.1; Earth Observatory of Singapore; Shearer: PREM table; USGS: interior of the Earth
- Screen 5: IRIS: shadow zone; IRIS: S-wave shadow; USGS: shadow zone; Brush (1980); NASA Goddard; APS News
- Screen 6: Natural History Museum; Kansas Geological Survey; UCLA Meteorite Museum; WA Museum; Australian Museum; Museums Victoria; Museums Victoria: Murchison; NT Parks: Henbury; Museums Victoria: Henbury; Henbury plan of management (2002); Shoemaker and others (2005); Hamacher and Goldsmith (2013); NASA Earth Fact Sheet; Lumen Learning
- Screen 7: Panchuk (2019) chapter 3; Britannica: continental crust; Earle (2019) 18.2; NOAA (1996); Wilde and others (2001); Anzellini and others (2013)
- Screen 8: Earle (2019) 9.2; Britannica: geothermal gradient; Panchuk (2019) 3.3; KamLAND (2011); Davies and Davies (2010); BBC Science Focus; Wyborn and others (2005); Geoscience Australia: geothermal; Neumann and others (2000)
- Screen 9: USGS: hotspots; USGS: Volcanoes of Hawaii; USGS Volcano Watch; NOAA: Hawaiian data table; Davies and others (2015); ANU via Phys.org; Geoscience Australia: plate movement; Earle (2019) 10.4; Earle (2019) 10.5; Forsyth and Uyeda (1975); USGS: unanswered questions; Stock (2006)
- Teacher notes: POGIL Project; POGIL roles; UT Arlington; Walker and Warfa (2017); Vishnumolakala and others (2017); Hu and others (2016); NAGT misconceptions; Pickard and others (2011); Science Network WA (2014); The Conversation (2016)