Rocks Flashcards
What is geology?
Geology is the study of the Earth the materials of which it is made, the structure of those materials and the processes acting upon them. It includes the study of organisms that have inhabited our planet. An important part of geology is the study of how earths materials have changed over time.
What is a rock?
A rock is a mixture of minerals. A mineral is a natural compound. It has a chemical name and formula like the compounds in science. But we use it’s geological name. Minerals usually exist in rocks as crystals of various kinds shapes and sizes.
Three words to describe sedimentary rocks?
Colourful
Rough
Layered
How are sedimentary rocks made?
They are made when sediments get deposited at the bottom of seas, lakes. These sediments include eroded rock, skeletons etc. They build up.
Two examples of sedimentary rocks
Limestone
Sandstone
Three words to describe metamorphic rocks
Squashed
Resisting
Hard-wearing
How are metamorphic rocks made?
They are made when they are exposed to heat or pressure
Two examples of metamorphic rock
Marble
Slate
Three words to describe igneous rocks are
Hard
Resistant to weather and erosion
Shines when polished
How are igneous rocks made?
They are made when magma from inside the earth cools and solidifys to make rocks
Give two examples of igneous rocks
Granite
Basalt
What is the earths time scale
The geological time scale is a record of the life forms and geological events in earths history. Scientist developed the timescale by studying rock layers and fossils world wide. Radioactive dating helped determine the divisions in the time scale.
Give the order of the time scale from the earliest to the latest
Quartenary Neogene Palaeogene Cretaceous Jurassic Triassic Permian Carboniferous Silurian Ordovician Cambrian Precambrian
What happened in the Cretaceous period?
Chalk is formed in the Cretaceous Period as this is when warm tropical seas were present around the shores of the UK.
What happened in the Carboniferous period?
In the Carboniferous period there were tropical conditions in the uk because of the limestone and coal.
The rock cycle
A rock gets deposited in a river with layers and rock particles. Compaction and cementation causes the layers to be pressed and stick together. This is a sedimentary rock. The rock gets pushed underground. The rock gets put under a lot of heat and pressure so then it turns into a metamorphic rock. The metamorphic rock melts and turns into magma. If the magma stays underground and hardens it would be called an intrusive igneous rock and it would slowly uplift to the surface. Or the magma would erupt out of a volcano and then harden this would be called an extrusive igneous rock. The igneous rock gets weathered and eroded, it gets deposited at the bottom of a river and becomes a sedimentary rock to start the cycle all over again.
What is weathering?
Weathering is the breaking down of a rock by the action of things in its environment e.g. heat, cold, rain, plants, chemicals etc.
What is erosion?
Erosion is the wearing away of rock, stone ans soil by rivers, waves, winds or glaciers.
Rocks in the UK
The UK has a wide range of rock types found in different environments. This is because the land has been on a long journey. Events along the journey explain our mountains. As it moved around the land that is now the UK gathered sediments in many different environments over millions of years. So the UK has a range of sedimentary rocks from different ages.
Why does the UK have so many mountains?
It has lots of collision boundaries.
How do the age of rocks change as you go from North to South of Britain?
The south gets younger.
What is physical weathering?
Physical weathering is caused by the effects of changing temperatures on rocks causing the rock to break apart the process is sometimes assisted by water.
Freeze thaw is a type of physical weathering, explain it
Freeze thaw occurs when water continuously seeps into cracks, freezes and expands, eventually breaking the rock apart.
Exfoliation is the type of physical weathering, explain it
Exfoliation occurs as cracks develop parallel to the land surface a consequence of the reduction in pressure during uplift and erosion.
What is chemical weathering?
Chemical weathering is caused by the rainwater reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts. These reactions occur particularly when the water is slightly acidic.
Solution is a type of chemical weathering, explain it
Solution is the removal of rock in solution by acidic rainwater. In particular, limestone is weathered by rain water containing dissolved carbon dioxide this process is sometimes called carbon action.
Oxidation is a type of chemical weathering, explain it
Oxidation is the breakdown of rock by oxygen and water often giving iron rich rocks a rusty coloured weathering surface.
What is biological weathering?
Biological weathering is when living organisms contribute to the weathering process in many ways.
Types of biological weathering
- Trees put down roots through joints or cracks in the rock to find moisture as the tree grows. The roots gradually prise the rock apart.
- Burrowing animals such as moles and rabbits can also make cracks bigger.
- Lichens, algae and mosses can produce weak acids which open cracks in rock and expose them to chemical and mechanical erosion
How does physical weathering occur?
Through repeated melting and freezing of water (mountains and tundra) also expansion and contractions of the surface layer of rocks that are baked by the Sun (hot deserts).
