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Questions and Answers
What primarily causes sedimentation to occur?
What primarily causes sedimentation to occur?
Which type of sedimentary rock is formed from the weathering of existing rocks?
Which type of sedimentary rock is formed from the weathering of existing rocks?
What is the main process by which chemical sedimentary rocks form?
What is the main process by which chemical sedimentary rocks form?
Which of the following characteristics is NOT typical of chemical sedimentary rocks?
Which of the following characteristics is NOT typical of chemical sedimentary rocks?
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What type of sediments contribute to the formation of organic sedimentary rocks?
What type of sediments contribute to the formation of organic sedimentary rocks?
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How do metamorphic rocks primarily form?
How do metamorphic rocks primarily form?
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What is the primary characteristic of igneous rocks that results from the minerals they contain?
What is the primary characteristic of igneous rocks that results from the minerals they contain?
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How are intrusive igneous rocks primarily formed?
How are intrusive igneous rocks primarily formed?
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What distinguishes extrusive igneous rocks from intrusive ones?
What distinguishes extrusive igneous rocks from intrusive ones?
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Which process describes the movement of small particles of weathered rock by wind, water, and ice?
Which process describes the movement of small particles of weathered rock by wind, water, and ice?
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What effect do water and the chemicals in the water have on rocks?
What effect do water and the chemicals in the water have on rocks?
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Study Notes
Igneous Rocks
- Igneous rocks form when magma cools.
- Fast cooling results in fine crystals.
- Medium cooling produces medium-sized crystals.
- Slow cooling leads to large crystals.
- Extrusive igneous rocks form when lava cools above ground.
- Intrusive igneous rocks form when magma cools beneath the Earth's surface.
- Examples of intrusive rocks: pluton, sill, dike, laccolith, batholith, xenolith
- Examples of extrusive rocks: ash and lava, parasite cone
Characteristics of Igneous Rocks
- Igneous rocks are hard due to the hard minerals they contain.
- Igneous rocks are strong due to the interlocking mineral crystals.
- The crystals interlock and lock together.
- Classification is based on how they formed and the rock's texture, and colour.
Intrusive Igneous Rocks
- Intrusive rocks form when magma cools slowly beneath the Earth's surface.
- "Intrusive" means "forced in".
- These rocks form between layers of other rocks, forced into existing rock layers by pressure.
- Intrusive rocks form large crystals.
- Pegmatite is a light-colored, very coarse-grained intrusive igneous rock.
- Pegmatite often contains rare minerals not found in other parts of the magma chamber.
Extrusive Igneous Rocks
- Extrusive rocks form when lava cools above ground.
- The lava cools quickly, so these rocks form small crystals or no crystals at all.
- Obsidian is a dark-colored volcanic glass.
- Obsidian forms when molten rock material cools very rapidly.
- No crystals form in obsidian.
Weathering
- Weathering is the physical or chemical breakdown of rocks.
- Physical weathering is caused by: temperature change, ice and water, crystallisation of salts, wind, and living plants.
- Chemical weathering is caused by water and chemicals in the water and air reacting with rocks.
Erosion and Sedimentation
- Erosion is the process where small weathered rock particles are carried away by wind, water, or ice.
- Sedimentation is the process where eroded rock particles are deposited in a specific location.
- Sedimentation usually occurs where the moving water, wind or ice slows down.
Sedimentary Rocks
- Sedimentary rocks are made from sediments.
- Sediments are cemented together under pressure.
- Sedimentary rocks are classified by the type of sediment.
- Sediments can include pieces of weathered rock, minerals crystallizing in solution, and dead plant or animal material.
- There are three main types of sediments: clastic, chemical, and organic.
Weathered Rock Sediments
- Weathered rock sediments form clastic sedimentary rocks.
- Natural cements (chemicals in water) surround sediments, holding them together.
- Pressure from overlying sediment layers squeezes out water, causing cement to solidify.
Chemical Sediments
- Chemical sedimentary rocks form when dissolved materials come out of solution, forming a solid and sinking to the bottom.
- This process is called crystallisation.
- Dissolved minerals turn into solid crystals as water evaporates.
- Chemical sedimentary rocks contain crystals, are quite soft, rarely have layers, and some have fossils.
Organic Sediments
- Organic sedimentary rocks form when dead plant or animal matter accumulates and is cemented together.
- Organic sedimentary rocks can be layered.
- Most organic sedimentary rocks are soft, but some can be hard.
- Coal is an example of an organic sedimentary rock.
Uses of Sedimentary Rocks
- Sedimentary rocks have many uses due to their variety.
- Sandstone is used in buildings, walls and pavers.
- Limestone is used to make cement, glass, and steel.
- Gypsum is used to make plaster.
- Coal is used as an energy source.
Metamorphic Rocks
- Metamorphic rocks form when high temperatures and pressure alter existing igneous or sedimentary rocks.
- Changes can be physical or chemical.
- New minerals might form that weren't in the original rock.
Types of Metamorphism
- Regional metamorphism occurs over a wide area due to deep underground heat and pressure or tectonic plate movement.
- Contact metamorphism that occurs around magma in local areas.
Types
- Metamorphic rocks are formed through burial, contact with magma, and regional metamorphism.
Rock Cycle
- The rock cycle describes the continuous process that transforms the three main rock types (igneous, sedimentary, and metamorphic) into one another over geological time.
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Description
Explore the fascinating world of igneous rocks in this quiz, which covers their formation, types, and characteristics. Learn the differences between intrusive and extrusive rocks and discover examples of each. Test your knowledge on the properties that make igneous rocks unique and vital to our planet.
