Rocks Igneous Metamorphic Sedimentary

What is a Rock? A rock is composed of minerals Can be made of organic material Solid material that forms Earth’s hard surface.

Igneous Rock

Rock that crystallizes from cooling of magma (inside Earth) or lava (on/outside surface of Earth) Characterized two ways – INtrusive or Extrusive Geology Kitchen Video - Igneous Rocks

Crystallizes inside of Earth from magma Magma cools slowly (because of the blanket of the Earth’s layers) Intrusive Igneous Rock

Intrusive Igneous Rock (continued) Cooling slowly = large interlocking crystals (usually two or more colors) Large crystals = coarse-grained texture Devils Tower, Wyoming

Igneous Intrusive Rock Samples Granite Note 3 minerals = mica (black) quartz (smoky) feldspar (pink)

Extrusive Igneous Rock Crystallizes outside of Earth from lava – mostly from volcanic activity Lava cools quickly Cooling quickly = tiny or no mineral grains (usually one drab color)

Extrusive Igneous Rocks (Continued) Tiny or no mineral grains = fine- grained texture EXTRA : Sometimes has pores or holes from trapped gases

Extrusive Igneous Rock Samples Pumice Basalt (seafloor) Obsidian (volcanic glass) (volcanic glass) Notice the very smooth texture Notice the drab color Notice the holes or pores

Mafic vs Felsic Mafic igneous rocks - dark in color and have a high density due to high quantities of heavy elements (magnesium, iron, calcium and sodium) –basalt (extrusive) and gabbro (intrusive). Felsic igneous rocks – light in color and have a lower density due to high quantities of lighter elements (silicon, oxygen, aluminum, sodium and potassium) –Pumice (extrusive) and granite (intrusive)

Sedimentary Rock How does Sedimentary Rock form? Click on image for video clip

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Sedimentary Rock Formed at surface of Earth (in lakes, oceans, rivers) in thin or thick layers (strata) Layering is referred to as stratification Formed from Cementation & Compaction of sediments or Evaporation/Precipitation Only rock type to contain fossils – one exception = volcanic ash Characterized two ways – clastic or non- clastic

Sedimentary Rock Strata

Clastic Sedimentary Rock Mineral grains (sediments/fragments) are compacted and cemented together. Example – sand compacted and cemented = sandstone Example – mud/clay compacted and cemented = shale Example – pebbles, sand and mud compacted and cemented = conglomerate Geology Kitchen Video – Clastic Sedimentary RockGeology Kitchen Video – Clastic Sedimentary Rock

Clastic Sedimentary Rock Samples sandstone shale field

Non-clastic Sedimentary Rock Two types – Organic Non-clastic or Chemical Non-clastic Organic – made from once living things – plants (coal) or animal life (fossil rich limestone - coquina) Chemical – made from evaporation (gypsum) or precipitation – (CaCO 3 – chemical limestone) Geology Kitchen Video – Chemical and Biologic Sedimentary RockGeology Kitchen Video – Chemical and Biologic Sedimentary Rock

Non-clastic Sedimentary Rock Samples Coal - organic Fossil rich limestone - organic Chemical limestone Gypsum - chemical

Sedimentary Features Ripple Marks – left by water or wind in sand, mud, etc. – can be preserved as a rock feature

Sedimentary Features Mud cracks in today’s puddles can be preserved as rock millions of years from now

Sedimentary Features Cross bedding – formed in old sand dunes or on off-shore sand bars

Metamorphic Rock How is metamorphic rock formed?

Metamorphic Rock Formed deep inside the Earth from intense heat and pressure Any rock type can be changed by metamorphism – depends on how much heat, pressure and original rock type to determine the outcome No melting involved – solid state process (more like softening) Hardest of three types of rock Characterized two ways – foliated or non- foliated Geology Kitchen Video - Metamorphism

Foliated Metamorphic Rock Banding (stripes) or cleavage (flaky) is present Always a change structure and texture of original rock and sometimes a change in the composition. When composition changes – most often a semi to precious gem can be formed. Animation of metamorphism forming foliated rockAnimation of metamorphism forming foliated rock Generally created from a rock that had more than one color.

Foliated Metamorphic Rock Samples schist Gneiss (Previously granite) Slate (previously shale)

Non-foliated Metamorphic Rock NO Banding and/or NO cleavage Change in structure and texture of original rock Possible change in composition. Generally created from rocks with only one color

Non-foliated Metamorphic Rock Samples Quartzite (previously sandstone) Marble (previously limestone)