Geology Test Revision
- 2. Igneous rocks are made in a volcano, from magma (Liquid Rock, which is underground). There are different types of Igneous Rock. If they cool outside of a volcano, they will cool quickly. These are called Extrusive igneous rocks and you can see small crystals in the rock. If a rock cools inside a volcano, it will cool slowly. This is called an Intrusive igneous rock and you can see large crystals in the rock.
- 3. • Basalt • Granite • Pumice • Obsidian • Gabbro
- 4. The first step is called Sedimentation. This is where rocks build up a first layer, this happens by the river transporting them and leaves rocks on the rive bed. Sedimentary Rocks are formed by different layers of rock being squashed together. This is called compaction. This process squeezes the water away, leaving salt crystals that cement the rocks together. (Cementation)
- 5. • Chalk • Limestone • Sandstone • Shale
- 6. Metamorphic rocks are made far underground, after the sedimentary rocks are buried by earth movements. The rocks are heated up by magma and are put under lots of pressure. They don’t melt, but the minerals contained in the rock are chemically changed, meaning that they are no longer sedimentary rocks – but metamorphic rocks.
- 7. • Marble – Formed from Limestone • Slate – Formed from Shale
- 8. The three types of Weathering are:
- 9. 1. Physical Weathering – There are multiple types of physical weathering, one of them is the Freeze-Thaw process. When there is a crack into a rock, rainwater flows in. The water freezes in the cold, and makes the crack wider. The ice melts. The water gets further into the crack, making it bigger. This freezing and then thawing process continues until the crack gets so big and a large chunk of rock breaks off.
- 10. Biological Weathering – Life like animals and plants can wear away rocks. This is Biological Weathering. E.g plants could grow through cracks, pushing cracks wider, and apart. Or, animals can burrow into cracks, making them wider and deeper. Even people can cause biological weathering by walking through country paths. Boots wear away the pathway.
- 11. Chemical Weathering is where rocks are worn down chemically. The chemicals are usually from rainwater, which contains a little acid naturally, where carbon dioxide dissolves in it. The rocks react to the chemicals are wear away gradually. Rocks that are Weathered by chemicals easily: • Limestone • Chalk These rocks are weathered easily because they are made of a mineral called calcium carbonate. So, when acidic rainwater falls, a chemical reaction happens. New soluble substances are formed during this process. These get washed away and the rock is weathered. Rocks that are not easily Weathered by chemicals: • Granite • Gabbro These are hard rocks that weather slowly. Although, some of their minerals do react to the rainwater. New, weaker substances are formed and they crumble away.
- 12. When substances like coal, natural gas, and oil are burned, sulphur dioxide and carbon dioxide are released into the air. When the chemicals dissolve in the clouds, the rainwater becomes much more acidic than usual. This is known as ‘acid rain’. Acid Rain speeds up the process of chemical weathering, as the acid is much more powerful. Acid rain damages statues and buildings that are made of rock, especially limestone. Acid rain also kills fish and trees.
- 13. The rock is weathered somehow. A part of the rock/cliff would break away. Erosion happens when the pieces of rock fall off a cliff (Erosion = Is the movement of the broken pieces away from the site of weathering. Then, the rocks can be transported by rivers or streams. However, slow moving rivers can only transport small pieces of rock. When the rocks travel down rivers, they bash against each other and the river bed and become much smaller in the process.
- 14. • Construction • Medicines • Fuels • Sea walls • Granite – Kitchen worktops • Pathways • Limestone bricks They all depend on rocks and minerals.
- 15. Fossils are normally only found in Sedimentary rocks. This happens when an animal or plant died and became trapped under layers of rock and the skin (if an animal) would decompose. Only bones would be left and they would be an imprint in the rock. If a metamorphic rock was formed from a Sedimentary rock, there could be fossils, but the fossil would probably be squashed out of shape.
- 16. These Minerals must be supplied by our diet. Major Minerals • Calcium • Chloride • Magnesium • Potassium • Phosphorus • Sodium • Sulphur Major minerals are found in our body in amounts more than 5 grams. Trace Minerals • Chromium • Copper • Fluoride • Iodine • Iron • Manganese • Selenium • Zinc Trace Minerals are found in our body in amounts more than 5 grams.
- 17. Earth’s rocks don’t stay the same forever. Weathering and large earth movements can change rocks, and they are gradually recycled over millions of years.