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Transcript of Metamorphic Rocks
The work metamorphic comes from the Greek word meta, meaning "change",and morphosis, meaning "form".
How They Form
Heat and pressure deep beneath the earth's surface can change any rock (Including igneous, sedimentary, or another metamorphic rock) into a metamorphic rock.
Metamorphic rocks form when an existing rock is changed by heat, pressure, or chemical reactions. Most metamorphic rock forms deep underground.
When rocks change into metamorphic rocks their appearence, texture, crystal structure, and mineral content change.
Collosions between the earth's plates can push the rock under the earth's crust down torwards the heat.
Pockets of magma rising through the earth's crust also provides heat that can make metamorphic rocks.
The deeper a rock is pushed into the earth the greater the pressure is on it
When a rock is at a high temperature and there is a lot more pressure on it than usual the rock's minerals can be changed into other minerals; then it turns into a metamorphic rock.
Did you know that the process can happen without the rock itself melting?
But if it does melt magma is formed (igneous rocks) and the rocks cycle starts all over again
Types of Metamorphic Rocks
While a metamorphic rock is forming, high temperatues change the size and shape of it's mineral crystals
Tons of pressure in one direction on a rocks mineral grains squeezes the rock so tightly that the mineral grains line up in flat, parellel layers
When temperatures are high but the pressures are pretty low and equal in all directions the minerals are arranged randomly in the rock
Did you know that geologists can learn the following about the earth from the study of metamorphic rocks:
the temperature and pressure conditions (metamorphic enviroment) in which the rocks were formed
the composition of the parent, or original unmetamorphosed rock
aids in the interpretation of the plate tetonics setting in which metamorphism took place
aids in the reconstruction of the geological history of an area
Geologists classify a metamorphic rock according to its arrangement of the grains that make it up.
Metamorphic rocks that have their grains arranged in straight, parellel layers are called foliated rocks
The term foliated comes from the Latin word leaf. It describes the flat, thin layers that are found in mostly all metamorphic rocks
Some foliated rocks including- schist, slate, and gneiss- sometimes split apart along the layers
Examples of Foliated Rocks
Examples of Nonfoliated Rocks
composed of the mineral quartz,
it is found in a variety of different colors
this rock is extremely hard
quartzite is much smoother than sandstone
composed of the mineral calcite;
it is white and grey
marble has a fine, even grain
the crystals in granite(igneous rock) are flattened out by heat and pressure to turn into the foliated texture of gneiss
shale(sedimentary rock) is
turned into slate by heat and
sandstone(sedimentary rock) is
formed into quartzite by heat and
limestone(sedimentary rock) is
turned into marble by heat and
gneiss is made up of alot of quartz and feldspar minerals
it can be white, blue, black, or grey
it has a bumpy texture from when the granites minerals were broken down
slate is made up of clay and micas
it can also contain quartz, feldspar, calcite, pyrite, and hamatite
it is usually found in the color dark gray but it can also be green, red, black, purple, or brown
slate is a fine-grain rock that is not very rough and can be carved into a smooth surface
Metamorphic rocks that that have their grains arranged randomly are called nonfoliated rocks
Any metamorphic rock that is nonfoliated can not split into layers because of how its grains are arranged
Some common nonfoliated rocks include marble and quartzite
Since there are two types of metamorphic rocks (foliated and nonfoliated) geologists look for the characteristics of those two types.
If they see a rock thats minerals and colors look like they are organized in strips or layers they then know that it is a metamorphic rock because it is foliated.
If they see a rock thats minerals and colors look like they are organized in a random position they then know it is a metamorphic rock because it is nonfoliated.
Some metamorphic rocks can have an arrangement of colors while other rocks have only been found in one color.
Metamorphic rocks can harden during the changing process or soften during the changing process.
Its texture and look depends on if it has a coarse grain or a fine grain.
If it has a coarse grain you can see its minerals without using a magnifying glass and it is often bumpy.
If it has a fine grain the grains are very small and you can't even tell what its minerals are even using a magnifying glass. It makes it not bumpy but scratchy and rough.
How to Identify
where You Might Find
On Display And What They Are Used For
Some metamorphic rocks are important materials for building and sculpting. Marble and slate are both very common and they are useful materials.
Slate is useful because it is used for many different things and you can find it almost anywhere. Since it is foliated it can split into flat smooth pieces. Then the pieces can be usd for roofing, flooring, outdoor walkways and paths, chalkboards, and as a trim for some stone buildings.
Marble is useful because it is used for many different things and you can find it almost anywhere. Since marble has a fine, even grain, it can be cut into thin slabs and carved into tons of shapes. It is also easy to polish so it can stay very white if it needs to. Because of these things many people like to use marble for many buildings and statues.
It is also used for:
The Lincoln Memorial in Washington D.C. is made out of marble and the Statue of Abraham Lincoln that sits outside of it is also made out of marble.
Cousin Anna's Notes
Well, that's all!!!!!
Thanks for watching!!!!!
I hope you learned something!!!!!