- Describe how metamorphic rocks are shaped.
- Describe the properties of some widespread metamorphic rocks.
- Relate some widespread makes use of of metamorphic rocks.
Metamorphic rocks begin off as igneous, sedimentary, or different metamorphic rocks. These rocks are modified when warmth or stress alters the prevailing rock’s bodily or chemical make up. One methods rocks might change throughout metamorphism is by rearrangement of their mineral crystals. When warmth and stress change the atmosphere of a rock, the crystals might reply by rearranging their construction. They’ll type new minerals which can be extra steady within the new atmosphere. Excessive stress may result in the formation of foliation, or flat layers in rocks that type because the rocks are squeezed by stress. Foliation usually kinds when stress was exerted on a rock from one route. If stress is exerted from all instructions, then the rock often doesn’t present foliation.
There are two predominant varieties of metamorphism:
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- Contact metamorphism—happens when magma contacts a rock, altering it by excessive warmth (Determine 4.14).
- Regional metamorphism—happens when nice lots of rock change over a large space on account of stress exerted on rocks at plate boundaries.
It is very important notice that metamorphism doesn’t trigger full melting of the preliminary rock. It solely causes modifications to a rock by warmth or stress. The rearrangement of the mineral crystals is the commonest method that we discover these modifications. Desk 4.3 exhibits some widespread metamorphic rocks and the unique rocks that they arrive from.
Desk 4.3: Widespread Metamorphic Rocks Image Rock Title Kind Feedback Slate Foliated Metamorphism of shale Phyllite Foliated Metamorphism of slate, however beneath larger warmth and stress than slate Schist Foliated Usually derived from metamorphism of claystone or shale; metamorphosed beneath extra warmth and stress than phyllite Gneiss Foliated Metamorphism of assorted totally different rocks, beneath excessive circumstances of warmth and stress Hornfels Non-foliated Contact metamorphism of assorted totally different rock varieties Quartzite Non-foliated Metamorphism of sandstone Marble Non-foliated Metamorphism of limestone
Hornfels, with its alternating bands of darkish and lightweight crystals is an efficient instance of how minerals rearrange themselves throughout metamorphism. On this case, the minerals separated by density and have become banded. Gneiss kinds by regional metamorphism from each excessive temperature and stress.
Quartzite and marble are essentially the most generally used metamorphic rocks. They’re regularly chosen for constructing supplies and paintings. Marble is used for statues and ornamental gadgets like vases (Determine 4.15). Floor up marble can be a part of toothpaste, plastics, and paper. Quartzite may be very laborious and is commonly crushed and utilized in constructing railroad tracks (Determine 4.16). Schist and slate are generally used as constructing and panorama supplies.
- Metamorphic rocks type when warmth and stress rework an current rock into a brand new rock.
- Contact metamorphism happens when sizzling magma transforms rock that it contacts.
- Regional metamorphism transforms massive areas of current rocks beneath the great warmth and stress created by tectonic forces.
- Why do the minerals in a rock generally rearrange themselves when uncovered to warmth or stress?
- What’s foliation in metamorphic rocks?
- Describe the totally different circumstances that result in foliated versus non-foliated metamorphic rocks.
- Record and describe the 2 predominant varieties of metamorphism.
- How can metamorphic rocks be a clue to how they have been shaped?
- Suppose a phyllite pattern was metamorphosed once more. How would possibly it look totally different after this second spherical of metamorphism.
contact metamorphism Outcomes from temperature will increase when a physique of magma contacts a cooler current rock. foliation Property of some metamorphic rocks during which flat layers are shaped; seen as proof of compressing by stress. regional metamorphism Happens when nice lots of rock change over a large space on account of stress. steady Regular and never prone to change considerably any extra.
Factors to Think about
- What kind of plate boundary would produce essentially the most intense metamorphism of rock?
- Do you assume new minerals may type when an current rock is metamorphosed?