There are three main types of rocks: igneous, sedimentary, and metamorphic. Igneous rocks form from cooling magma underground or lava on the surface. Sedimentary rocks form from compressed fragments of other rocks or organic matter. Metamorphic rocks were already existing rocks that underwent extreme pressure, heat, or chemical changes and altered form. Rocks are constantly changing between these types through the rock cycle as geological forces cause one type of rock to transform into another over long periods of time.
2. Three Major Types of Rocks
• Igneous Rocks: “meaning from
fire”
– Formed when magma cools and
hardens.
– Magma is called lava when it
reaches the earth’s surface.
3. Three Major Types of Rocks
• Sedimentary Rock:
– All types of rock, minerals, and
organic matter that have been
broken into fragments by forces.
• Wind, water, ice
– Deposits harden after being
compressed together.
4. Three Major Types of Rocks
• Metamorphic Rock: “changed
form”
– When an existing rock undergoes
extreme forces it changes form.
• Tremendous pressure
• Extreme heat
• Chemical processes
5. The Rock Cycle
• A cycle is a series of changes
– Geological forces and processes cause rock to
change from one type to another and back again.
– Rocks in the crust have passes through the cycle
many times.
