Introduction to Geology Chapters 13-15

The Earth’s Structure Inner core: solid core of iron and nickel, 9000-11,000 degrees F Outer core: liquid layer of iron and nickel, 7200-9000 degrees F Mantle: Lithosphere – upper mantle (solid) plus crust, forms rocky plates that make up earth’s surface Aesthenosphere – below lithosphere, softer Lower mantle: semi-liquid rock, material rises and sinks

Mohorovicic discontinuity (the Moho) – slippery layer in the lithosphere that forms the boundary between the crust and the mantle Crust: outer layer, solid, about 7 miles thick

Rocks

Three types of rocks Sedimentary – Eroded sediments are carried by water, then drop and are compacted by heat and pressure. Igneous – Formed by the cooling of molten rock Metamorphic – Sedimentary, igneous, or other metamorphic rocks that have been changed by heat and pressure into a new kind of rock

Sedimentary Rocks Most common type of rock Typically form layers called strata Two types: clastic and non-clastic

Clastic Sedimentary Rocks Appear to contain fragments eroded from other rocks Form when rocks get broken up then cemented together with heat and pressure Examples: conglomerate, sandstone, shale

Nonclastic Sedimentary Rocks Form from minerals dissolved in water Examples: limestone and halite

Fossils and Sedimentary Rock A fossil is any trace or remains of a living organism that has been preserved by natural means. Fossils are almost always found in sedimentary rock. Why?

Fossil Fuels Appear to come from fossilized remains of plants and animals Can be solid, liquid, or gas.

Coal Sedimentary rock that appears to have been laid down by water. Appears to have been formed rapidly by plant life being deposited under large quantities of flowing water. Heat and pressure changed them to rock.

Oil Liquid fossil fuel formed from ocean-dwelling creatures Found with sedimentary rocks of marine origin, sometimes with marine fossils in them

Natural Gas Gaseous fossil fuel often found with oil May be a by-product of oil formation

Where fossil fuels are found

Igneous Rocks

Igneous rocks Appear to have been molten in the past Magma – molten rock found beneath earth’s surface Lava – molten rock that flows out onto earth’s surface

Two types of igneous rocks Extrusive – formed when lava solidifies above earth’s surface Intrusive – formed when magma solidifies after squeezing into other rocks

Metamorphic Rocks

Metamorphic rocks Appear to have changed in structure or chemical composition since their formation

Two types of metamorphic rock Foliated – banded or layered Nonfoliated – no bands or layers