Rock Types
Igneous, Sedimentary, Metamorphic
Igneous rocks make up 95% of the rocks of the crust of Earth. They are also some of the oldest rocks that are found at the surface of Earth.
Igneous rocks form from molten rock which is either ejected at the surface of Earth or cools off underground. When volcanoes erupt, they can eject molten rock.
Extrusive Igneous Rock• Extrusive means to stick out. Extrusive
rocks form when they cool at the Earth’s surface. Because of their rapid cooling, they have smaller crystals.
Extrusive rocks that cool quickly have very small crystals.
Obsidian is a good example of a very quickly cooled extrusive igneous rock. It appears glass-like.
Sometimes when an extrusive rock is cooled very quickly and has lots of
air pockets we get pumice or scoria.
Pumice
Scoria
Intrusive rock cools under the surface. It has more time to
cool and forms larger crystals.
GraniteDiorite
Quartz
Sedimentary rocks are the result of the processes of weathering and
erosion which are continually breaking down and rearranging them. Small rocks, fragments and organic
remains that have been moved by water, wind or other agents of erosion are called
sediment. Over a period of time, sediment is cemented together.
Sandstone
Sedimentary rocks can be formed from metamorphic, igneous or other sedimentary
rocks that have been broken down by weathering. In nature sedimentary rocks are usually found in layers with the oldest
layer on the bottom.
Three types of Sedimentary Rocks• Clastic: made of broken pieces of other
rocks that are squeezed and cemented together. Sandstone
Shale
Breccia
Organic Sedimentary Rocks• Remains of plants and animals.
Limestone
Coal
Chemical Sedimentary Rocks• Dissolved minerals that crystallize by
precipitation or evaporation.
HaliteGypsum
Limestone
Metamorphic Rock
METAMORPHIC ROCK
Has this ever happened to you?
You take a peanut butter and jelly sandwich to school. You check your backpack at lunch
and find that your books have been sitting on the sandwich all day! The heat of the day and
pressure of the books have mushed the sandwich into a completely different shape.
Your lunch has experienced what rocks experience deep in the interior of Earth, the
process of metamorphism.
Rocks that have changed shape or composition due to intense heat and pressure are called metamorphic
rocks. • Metamorphic rocks are created from
sedimentary, igneous or other metamorphic rocks.
• They are formed deep inside the earth.
• Heat and pressure from the rock above AND below flatten and bend the rock.
HEAT & PRESSURE
Foliated or Non-foliated
SlatePhyllite
Schist
Gneiss
Quartzite
Marble
Shale + Heat & Pressure = Slate
Basalt + Heat & Pressure = Schist
Granite + Heat & Pressure = Gneiss
Limestone + Heat & Pressure = Marble
Sandstone + Heat & Pressure = Quartzite
Remember!
• Igneous rocks are formed by cooling of magma, either above or below the Earth’s surface.
• Sedimentary rocks are formed from broken pieces of other rocks (sediment) of all sizes.
• Metamorphic rocks are other rocks that are changed through heat and pressure.
What kind of rock is pumice?
Igneous? Sedimentary? Metamorphic?
Pumice is an igneous rock!
What kind of rock is quartzite?
Igneous? Sedimentary? Metamorphic?
Quartzite is a metamorphic rock!
What kind of rock is coal?
Igneous? Sedimentary? Metamorphic?
Coal is a sedimentary rock!
•Is coal a mineral????
What kind of rock is obsidian?
Igneous? Sedimentary? Metamorphic?
Obsidian is an igneous rock!
What kind of rock is halite (salt)?
Igneous? Sedimentary? Metamorphic?
Halite is a sedimentary rock!
What kind of rock is sandstone?
Igneous? Sedimentary? Metamorphic?
Sandstone is a sedimentary rock!
What kind of rock is limestone?
Igneous? Sedimentary? Metamorphic?
Limestone is a sedimentary rock!
What kind of rock is basalt?
Igneous? Sedimentary? Metamorphic?
Basalt is an igneous rock!
What kind of rock is gneiss?
Igneous? Sedimentary? Metamorphic?
Gneiss is a metamorphic rock!
Da Rock Cycle!