Year 8 Science · Unit 3 · Lesson 24
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Learning Goals
Order the steps
Number the events from 1 to 8 to show the correct order. Event 1 = what happened first.
| Order | Event |
|---|---|
| Compaction and cementation of sand grains form sandstone. | |
| The sandstone cliffs are shaped by water erosion along joint lines, forming gorges. | |
| Magma cools slowly underground, forming granite with large crystals. | |
| Rivers carry sand grains downstream and deposit them in layers. | |
| Uplift over millions of years brings the granite to Earth's surface. | |
| Weathering at the surface breaks the granite into smaller fragments and sand grains. | |
| Tectonic forces uplift the sandstone above sea level again. | |
| Sand layers are buried under more sediment, increasing pressure. |
Real-world context
A geologist is examining rock samples collected near Bathurst, NSW, in the central tablelands of New South Wales. One sample contains the remains of ancient marine shells preserved within the rock. The geologist knows the Bathurst region contains rocks from multiple geological periods, including sequences deposited during times when the area was covered by shallow seas.
(a) Identify what type of rock the fossil-containing sample must be, and explain why fossils can only be preserved in this rock type and not in igneous or metamorphic rocks.
(b) The fossil shells are marine (ocean) animals, but the sample was collected 200 km inland at 700 m elevation. What does this tell us about the environment where this rock formed millions of years ago?
(c) If this rock sample were buried 15 km underground under extreme pressure and heat (but did not melt), what would it become? Name the new rock type and give a specific example if the original rock was limestone.
Wrap Up
In one sentence, what was the main idea of this lesson?