GEO Exam 1 Review

Weathering

Weathering

The chemical and physical processes that break down rock at Earth's surface.

Erosion

Processes by which rock, sand, and soil are broken down and carried away (i.e. weathering, glaciation)

Deposition

Refers to processes by which sediment particles settle out as water currents slow, winds die down, or glacier edges melt to form layers of sediment in sink areas.

Burial

Layers of sediment accumulate in sink areas on top of older, previously deposited sediments, which are compacted and progressively buried deep within a sedimentary basin.

Diagenisis (lithification)

The physical and chemical changes— caused by pressure, heat, and chemical reactions—by which sediments buried within sedimentary basins are converted into sedimentary rock

Sediment rounding and sorting

Tendency for variations in current velocity to segregate sediments according to size

Continental Enviroments

Lakes, alluvial environment, desert, glacial

Shoreline Environments

Delta, Beach

Marine Environments

Shelf, reefs, deep-sea

Bedding

Layers of sediment with different particle sizes or compositions are deposited on top of one another.

Cross-Bedding

Layers of sediment deposited by wind or water and inclined at angles as much as 35 degrees from the horizontal. Form when sediment particles are deposited on the steeper, down current (leeward) slopes of sand dunes on land or sandbars in rivers and on the seafloor.

Ripples

Small ridges of sand or silt whose long dimension is at right angles to the current.

Bioturbation

Organisms churn and burrow through muds and sands.

Lithification

Compaction and cementation

Siliciclastic rocks

Conglomerate, sandstone, shale

Biological

Limestone

Atoll

Coral islands in the open ocean surrounding circular lagoons

Chemical

Evaporites

Intrusive igneous rocks

Coarse Crystals (Granite, Gabbro)

Extrusive igneous rocks

Lavas or pyroclastic rocks (Basalt, Rhyolite, Porphyry, Obsidian)

Felsic

Feldspar - Silica (Granite, Rhyolite)

Mafic

Magnesium - Ferric (Gabbro, Basalt)

Ultramafic

Peridotite

Intermediate

Granodiorite, Diorite, Dacite, Andesite

Melting (i)

Temperature increase (partial melting occurs)

Melting (ii)

Pressure decrease (decompression melting)

Melting (iii)

Addition of water

Where magma forms (i)

Formation of magma chambers in lithosphere cavities

Where magma forms (ii)

Temperature increase with depth in crust/mantle (not uniform)

Magmatic differentiation

One magma can crystallize into different rocks

Fractional crystallization

The process by which the crystals formed in a cooling magma are segregated from the remaining liquid rock.

Minerals

A naturally occurring, solid crystalline substance, usually inorganic, with a specific chemical composition.

Cleavage

A mineral's ability to split easily along flat surfaces.

Fracture

The tendency of a crystal to break along irregular surfaces other flat ones.

Quartz

Pure silicon and oxygen

Silicates

All of them contain silicate tetrahedral. Feldspars are very common.

Carbonates

Calcite and dolomite

Continental Drift Theory

By Alfred Wegener in 1915 (based on similar geologic features on opposite sides of the Atlantic)

Major Plates

African Plate, Arabian Plate, Eurasian Plate, Australian Plate, North American Plate, Indian Plate, Antarctic Plate

Divergent Boundaries

ocean-ocean

Convergent Boundaries

ocean-ocean, ocean-continent, continent-continent

Transform

continent-continent

Magnetic anomalies

The intensity of the magnetic field alternated between high and low values in long, narrow parallel bands.

Isochrons

Boundaries between magnetic anomalies are contours of equal seafloor age.

Oldest Seafloor

180 million years

Eratosthenes

250 BC, He calculated the circumference of the earth to be 40,000 km

Moho

Separates a crust composed of low-density silicates, which are rich in aluminum and potassium, from the higher-density silicates of the mantle, which contain more magnesium and iron.

Aethenosphere

The layer of the mantle just below the lithosphere; it is made of molten rock that moves very slowly due to convection currents

Earth's age

4.56 billion years

Oldest known rocks

4 billion years old

Oldest fossil bacteria

3.5 billion years old

Evolutionary "big bang"

542 million years ago