Landform Geography Earth’s Internal Structure, Rock Cycle, and Geologic Time

Earth’s Inner Structure Major Layers (outside-in): Lithosphere Upper Mantle Lower Mantle Outer Core Inner Core

Earth’s Interior

Lithosphere

The vast give-and-take at the Earth- atmosphere-ocean interface or cycling within the lithosphere –Fueled by the sun and Earth’s internal heat –Hydrologic Cycle –Rock Cycle –Tectonic Cycle The Geologic Cycle

Rock Cycle –Rock – assemblage of minerals bound together or a mass of a single mineral… –Minerals – inorganic, nonliving, natural compound having a chemical formula and crystalline structure

Igneous Rock Formed from cooled magma – liquid rock from asthenosphere Extrusive igneous rock – Intrusive igneous rock – Hypabyssal igneous rock -

Sources of Igneous Rock

Extrusive Igneous Rock Basalt - fine-grained, dark-colored extrusive igneous rock Rhyolite - fine- grained, dark-colored extrusive igneous rock

Intrusive Igneous Rocks Diorite – coarse-grained, intrusive igneous rock Gabbro – coarse-grained, intrusive igneous rock Granite – coarse-grained, intrusive igneous rock

Sedimentary Rock Vast amts of formerly loose minerals (sediment) deposited in layers Sediments cement to each other in process called lithification – 3 Types:

Clastic Sedimentary Rock Examples Siltstone Sandstone

Chemical Sedimentary Rock Formation Andros Island, Bahamas

Chemical Sedimentary Rock Examples Limestone - can also form chemically from the precipitation of calcium carbonate from lake or ocean water Rock Salt - forms from the evaporation of ocean or saline lake waters.

Organic Sedimentary Rocks Coal – from plant and organic matter deposited in cool wetlands, forming peat – over time overlying layers of sediment compress & heat peat into coal “Overcooked” deposits become petroleum Natural gas – from microscopic plants at surface of sea water – decompose to gas

Metamorphic Rocks From igneous & sedimentary rock under great heat & pressure for millions of years Examples of igneous & sedimentary rocks becoming metamorphic: –Shale → Slate → Schist –Limestone → Marble –Sandstone → Quartzite

Metamorphic Rock Examples Schist Slate Marble Quartzite

The Rock Cycle

Geologic Time Earth’s history (4.5 B years) divided into: –Eons Eras –Periods »Epochs Radiometric Dating – compare amt of radio- active isotope to amt of decayed end product in a rock to estimate its age

Geologic Time

Geomorphology of Continents and Ocean Basins Geomorphology – study of formation, shape, distribution, & evolution of landforms on Earth Landform – a distinct geographic feature such as a mountain, river valley, coastline, or sand dune Continents consist of 3 basic geomorphic regions: Alpine Chains, Continental Shelves, & Continental Shields

Continental Shelf Earth’s land area increases dramatically (from 29% to 35% of Earth’s surface) if sea level falls as in a previous glaciation (1.6 my ago) because of the relatively shallow continental shelf.

Continental Shields Geologically inactive regions with low relief made of old, stable, igneous or metamorphic rock

Alpine Chains Belts of active mountain building due to volcanic or tectonic processes