Reading rocks, Earth's layers and moving plates. Crystal size records how fast a rock cooled; a rigid outer shell rests on slowly flowing hot rock, and currents in the mantle carry the plates. Concept tutorials with a cross-section of the Earth and simulations of cooling magma and mantle convection.
How igneous rocks form, and what their crystals tell us (AC9S8U04).
Igneous rock forms when magma or lava cools. Slow cooling underground gives large crystals (granite); fast cooling at the surface gives small crystals (basalt) or glass (obsidian). Crystal size is a record of cooling rate.
A few quick questions on how sedimentary and metamorphic rocks form, how rocks change from one type to another, and why properties decide how rocks are used. Taught in class; use this to check yourself.
Earth's layers, the plates and what drives them (AC9S8U03).
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 lithosphere is broken into rigid plates that move a few centimetres a year. Slow convection currents in the hot mantle carry them, driven by Earth's inner heat: from the core below and from radioactive elements in the mantle rock itself.
A few quick questions on what happens where plates move apart, collide and slide past each other, and the evidence that plates move. Taught in class; use this to check yourself.
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