1. Rocks and the Rock Cycle
LEQ: How have different processes created the mineral and rocks that are found in Earth’s crust?

2. Rocks
Rocks are made of minerals from Earth’s crust and mantle.

3. Igneous Rocks
Also known as firestones because they form from either magma or lava.
Intrusive Igneous Rocks form below Earth’s surface (magma).
Cools slowly and form large mineral crystals
Ex: Granite, Diorite, Gabbro

4. Igneous Rocks
Extrusive Igneous Rocks form above Earth’s surface (Lava).
Cools quickly and forms small crystals or no crystals (glass).
Ex: Obsidian, Basalt, Rhyolite

5. Igneous Rocks
Along with crystal size, igneous rocks are also classified by color or mineral composition.
Mafic rocks are dark in color and usually contain the minerals OLIVINE OR CALCIUM PLAGIOCLASE.
Example: Basalt from the black beaches of Hawaii

6. Igneous Rocks
Intermediate rocks are dark and light in color (Dalmatian speckled).
Ex. Diorite
Felsic rocks are light in color and usually contain minerals quartz and muscovite (high in silica).
Ex. Rhyolite

7. Sedimentary Rocks
Formed from the processes of erosion, deposition, compaction, and lithofication.
Erosion: Breaking up and wearing down rocks.
Deposition: Rock sediments sinking to the bottom of lake, river, ocean, glacial deposits.
Compaction: Pressing sediments together.
Lithofication: Process where dissolved minerals crystallize and “glue” sediments together.

8. Classification of Sedimentary Rocks
Chemical Composition
Clastic: formed from the cementation (lithofication) of other rock sediments
Chemical: formed from precipitation out of solution.
Ex. Rock Salt or some forms of limestone (caves)
Organic: formed from the remains of once living creatures.
Ex. Coal, Coquina (special limestone from shells)

9. Classification of Sedimentary Rocks
Rock Type
Fragment Size
Breccia
Fragments are > 2mm(gravel) in size, fragments are jagged.
Conglomerate
Fragments are > 2mm (gravel) in size, fragments are rounded.
Sandstone
Fragments are 1/16-2mm in size
Siltstone
Fragments are1/16-1/256mm in size
Shale
Fragments are <1/256 mm in size (clay)
Mudstone
Composed of 50% shale and 50%silt
Limestone/Coquina
Formed from skeletons of corals and mollusks

10. Metamorphic Rocks
Form from heat and pressure applied to igneous, sedimentary or other metamorphic rocks.
Metamorphic Processes
Contact Metamorphism is when an igneous intrusion (magma) causes surrounding rock to “bake”.
Pressure is not a factor.

11. Metamorphic Rocks
Regional Metamorphism is when heat from pressure causes metamorphism.
Often seen in events such as continental collisions.

12. Types of Metamorphic Rocks
Foliated Rocks: Rocks that have grains arranged in parallel layers or bands.
Gneiss, Slate
Non-Foliated: Rocks that have mineral grains arranged randomly.
Marble or quartzite

13. Rock Cycle