Earth has layers: a thin solid crust, a thick solid mantle that flows very slowly, a liquid outer core and a solid inner core. Temperature and pressure rise with depth. The lithosphere (crust plus the rigid top of the mantle) is the rigid outer shell that breaks into plates.
The deepest hole ever drilled reached about 12 km. The centre of the Earth is 6371 km down. Everything we know about the rest comes from earthquakes.
Before plates can make sense, you need a picture of what they sit on.
Engage: Commit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Explore: Try it on the board and compare what happens with your prediction.
Explain: Use the particle model to explain what you saw.
Elaborate: Use the same idea in a new context.
Evaluate: Look back at your first ideas and what changed.
WidthMore contexts, same idea.
Make your prediction first. Help opens once you've locked it in.
EngageCommit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Engage: solid or liquid?
ExploreTry it on the board and compare what happens with your prediction.
Explore: cut a wedge
Click each layer to find out what it is. Drag the Depth slider down to the centre: watch the temperature and pressure. Then press Show it to scale.
Try it yourselfYour edits are saved in this browser.
Find all six layers and probe down to the centre.
Use the board. This ticks when you get there.
ExplainUse the particle model to explain what you saw.
Explain: layers and the lithosphere
In your book: draw a labelled cross-section of the Earth, mark the lithosphere and asthenosphere, and write the state of each layer.
Solid or liquid?
Crust
MantleSolid, but it flows very slowly over millions of years.
Outer core
Inner coreHotter than the outer core, but the enormous pressure keeps it solid.
Elaborate TypicalUse the same idea in a new context.
Elaborate: the skin of an apple
Elaborate WiderUse the same idea in a new context.
Elaborate: how do we know?
EvaluateLook back at your first ideas and what changed.
Evaluate: look back
Write one sentence: "At first I thought… Now I think… because…"
Revision summary
Crust (thin, solid) → mantle (thick, solid but flows very slowly) → outer core (liquid iron and nickel) → inner core (solid iron and nickel).
Temperature and pressure increase with depth.
The lithosphere (crust + rigid top of the mantle) is the rigid outer shell, broken into plates; it rests on the soft, slowly flowing asthenosphere.
For teachers
Students describe Earth's layers and their states, explain that temperature and pressure increase with depth, and identify the lithosphere as the rigid outer layer (AC9S8U03, node 1, a hinge node). About 20 minutes.
I can name Earth's layers and say whether each is solid or liquid.
I can explain that temperature and pressure increase with depth.
I can explain that the lithosphere is the rigid outer shell (crust and top of the mantle).
Before class
A concept tutorial for introducing or revising the idea. Set the width with ?width=minimum, typical (default) or wider.
The hinge misconception is a liquid mantle ("a sea of magma"). If the mantle were liquid, rigid plates wouldn't make sense. The board describes it as solid rock that flows very slowly.
Board notes: the default view enlarges the outer layers so they can be clicked; "Show it to scale" draws true thicknesses. Temperatures and pressures are rough textbook values joined smoothly (for example, about 1300 °C at the base of the lithosphere, about 5400 °C at the centre). Depths: continental crust about 35 km (oceanic about 7), lithosphere about 100 km, asthenosphere to about 350 km, core–mantle boundary 2890 km, inner core from 5150 km.
Running the lesson
Engage: count how many chose the sea of magma.
Explore: ask what surprised them in the to-scale view.
Explain: the lithosphere question is the checkpoint.
The hard part (on purpose)
Accepting a solid mantle that still flows. When a student says lava comes from a liquid mantle, ask where the board says melting happens.
When students get stuck
A student says lava comes from a liquid mantle. Ask: Where does the board say melting happens? Fix: Only in small pockets, where pressure drops or water is added: magma, not a whole liquid layer.
A student thinks the inner core must be liquid because it's hottest. Ask: What else increases with depth? Fix: Pressure: enough to keep it solid.
Stretch and support
Stretch: Australia sits on very old, stable lithosphere. Why might that mean few volcanoes and big earthquakes here?
Support: Give a cross-section outline with the layer names and states in a box to place.
Where it leads
Next: what moves the plates (node 2).
In class: a hard-boiled egg with a cracked shell as a model of the lithosphere (and where it breaks down).
What each step is for
Engage: solid or liquid?: Students who picture a molten mantle under the crust can't explain rigid plates; the board shows the mantle is solid rock that flows very slowly.
Explore: cut a wedge: Clicking each layer and probing temperature and pressure with depth builds the layered model; seeing it to scale shows how thin the crust really is.
Explain: layers and the lithosphere: Separating the rigid lithosphere from the soft asthenosphere below is the idea the plate model needs.
Elaborate: the skin of an apple: The to-scale view makes the thinness of the crust concrete.
Elaborate: how do we know?: Reasoning from seismic evidence shows how a model of something unseen is built.
Now you can
Name Earth's layers and say whether each is solid or liquid.
Explain that temperature and pressure increase with depth.
Explain that the lithosphere is the rigid outer shell (crust and top of the mantle).