GCSE Geography A Paper AF Geomorphic Processes (Types of Rocks) Learning outcomes: Describe the formation of the 3 types of rock Suggest characteristics of rocks Explain how sedimentary rock changes into metamorphic rock over time

Types of Rock To be able to understand Geomorphic processes, you need to learn the 3 types of rock before learning anything else There are 3 main types of rock: Igneous Rock Sedimentary Rock Metamorphic Rock These types of rocks have different features, for example they may be able to absorb water or not, and may contain crystals or fossils. Rocks that can absorb water are called Aquifers, and are what we call Permeable, for example Chalk Rocks that can not absorb water, and water flows on its surface is known as Impermeable, for example Concrete surfaces Igneous Rocks contain crystals, which vary in size depending on the time taken for magma to cool. Sedimentary Rocks and Metamorphic Rock contain fossils, but mostly sedimentary rock, see slide 4 for more info Figure 1: Slate Rock

Igneous Rocks Igneous rock forms underground, and on the surface, but is mostly found in the crust. Igneous rock forms when molten rock (Magma) cools into a solid state, for example the cooling of lava erupted from a volcano there are two types of igneous rock that you need to know: Intrusive Igneous Rock: Intrusive igneous rock forms when magma rises through cracks in the crust and cools, cooling slowly to form large crystals. Magma cools in magma chambers as well to form solid dome shape structures called Batholiths, the cracks in which the magma had flown and cooled in are called Dykes and Sill's, Dykes form when magma cools in cracks vertically and Sill's form when magma cools horizontally An example of Intrusive igneous rock is Granite Extrusive Igneous Rock: Extrusive igneous rock forms on the surface of the crust when molten rock is ejected out of a volcano, and cools quickly to create small crystals within the rock An example of Extrusive Igneous Rock is Basalt - Remember: Igneous Rock is an impermeable rock, water can not penetrate it Figure 2: Diagram of a Batholith Figure 3: A Sample of Granite

Sedimentary Rocks Sedimentary rock forms differently to Igneous Rock and Metamorphic Rock Sedimentary rock forms over thousands of years, where particles of sediment fall too the bottom of the sea from dead organisms, transported by erosion, over time these sediments build and compact by a process called Lithification to form sedimentary rock. Sedimentary rock overtime can overcome the surface of water, forming sea cliffs, which can eventually erode and weather. You need to know examples of how sedimentary rock can be compacted Limestone and chalk are formed from fossils and buried sediments of dead organisms over millions of years, where the fossils and sediment is buried deep underwater and compacted into a white rock substance, these rocks have the greyish colour from a compound called Calcium Carbonate. Other sedimentary rocks such as clay are formed from mud and clay particles, which compact on the sea bed over time, clay and shales are examples of rock found on shorelines - beaches Figure 4: Limestone sample

Metamorphic Rocks Metamorphic rock is formed from other types of rock, it is formed within the earths crust from intense heat and pressure acting on the rock. For example heat from the mantle which rises through the crust can heat up past sedimentary rock and change the shape and properties of rock into a different type of rock, for example limestone which changes into marble. Metamorphic rock can also be pressurised by the intense weight of other rocks acting above the rock, changing the state of the rock into a different shape. For example the formation of slate rock from clay Figure 5: Sample of slate rock Figure 6: Sample of Marble rock