Geology- The scientific study of the origin, history, and structure of the earth- The Science of the Earth

- Different disiciplines of Geology- Historical - discovers the past- Physical - understanding the processes that operate on and inside Earth

http://www.answers.com/Geology

Earth’s Internal Structure- Crust - The outermost solid layer of Earth- Mantel

- the thick shell of dense, rocky matter that surrounds the core - Core

- center & densest part - largely metallic iron

- Atoms of Elements -Formed in Solar Nebula

- Minerals -General chemicals compound formed by geological process

- Rocks - general combination of minerals - Core Fe + Ni - Mantle O + Si + Mg - Crust O + Si

Background: Geology

plate tectonics• theory that unifies many of the features and characteristics of continental drift and

seafloor spreading into a coherent model and has revolutionized geologists' understanding of continents, ocean basins, mountains, and earth history.

• plate tectonics theory holds that the lithosphere, the hard outer layer of the earth, is divided into about 7 major plates and perhaps as many as 12 smaller plates, c.60 mi (100 km) thick, resting upon a lower soft layer called the asthenosphere. Because the sides of a plate are either being created or destroyed, its size and shape are continually changing. Such active plate tectonics make studying global tectonic history, especially for the ocean plates, difficult for times greater than 200 million years ago. The continents, which are c.25 mi (40 km) thick, are embedded in some of

the plates, and hence move as the plates move about on the earth's surface.

Types of Plate Boundaries

Compression- compacts a block of rock & squeezes it into less space

- causes shortening - reverse fault- convergent boundary

Tension ( also called dilation)- Pulls a rock apart and inc. its length

Causes lengtheningNormal faultDivergent boundary

Shear-Smears a block of rock and may eventually tear it apart into blocks of

rock that slide past one of another along a strike-slip faultNeither lengthening or shorteningStrike-slip faultTransform boundary

Minerals• Inorganic, naturally occurring substances that have a characteristic chemical compound, distinctive physical properties and crystalline structure

• Crystalline structure•Is an orderly 3-D arrangement of atoms or moleculesGeneral. Mineral Properties

• Color•Luster

•Is a des. Of how mineral surfaces reflect light• Metallic

•Silvery, gold or brassy sheen•Nonmetallic

•Luster unlike that of metal

•Streak•Is color of substance after it has been ground to a fine powder

Metallic -Hematite

Hardness - Measure of resistance to scratching mohs scale of hardness

• Cleavage and Fracture – Cleavage surfaces occur as sets of parallel surfaces of weak

chemical bonding ( attraction) between repeating, parallel layers of atoms in a crystal

• Excellent cleavage– Direction reflects light in one direction from a set of obvious, lg, flat

and even surfaces• Good cleavage

– Directions reflects light in one direction from a set of many small, obvious, flat, but uneven surfaces

• Poor Cleavage– Direction reflects light in one direction from a set of flat, uneven

surfaces that are inconspicuous compared to the fracture surfaces» Most light is scattered randomly by the fractured surfaces

– Fractured surfaces of some irregular masses can be described as

• uneven • splintery (like splintered wood)• hackly ( jagged edges)

– conchoidal fractures• smoothly curved fractures• opal and pure quartz

Rocks

Igneous Rocks•are rocks that form when magma or lava cool to a solid form, either glass or masses of intergrown mineral crystals•Common Igneous Rock Textures

•Glassy •Completely lack grains

• Vesicular texture•Have bubbles•Have solutions cavities (cave-like spaces)•Fractures•Irregular spaces b/t poorly sorted grains of diverse size

•Randomly oriented small crystals: fine- grained crystalline texture•Grains gen. <1mm and too small to identify without a hand lens

•Randomly oriented large crystals: coarse-grained crystalline texture•Grains gen. >1mm & lg enough to identify unaided

•Extrusive vs. Intrusive•Extrusive

•Igneous rocks that form at the planets surface•Extruded or violently ejected onto the surface through volcanoes

•Intrusive•A body of magma that pushes its way into the Earth’s crust is Intrusive•Rocks that form by the cooling of intrusions

•Felsic vs. Mafic•Felsic

•Gen. light-colored•Quartz and potassium feldspar most abundant minerals

•Mafic•Dark-colored•Proxene and plagioclase most abundant minerals

Metamorphic Rocks• are rocks changed from one form to another (transformed) by intense hear,

intense pressure, or the action of hot fluids.• Common Metamorphic Rock Textures (p. 69)

• Crystalline texture: glittery when rotated in bright light– Equigranular crystalline texture

• Equingranular: all about the same size– Folded texture– Foliated small crystals and shiny reflection

• Foliated: layered alighnemnt of flat-sided mineral grains so they are parallel to one another giving the appearance of folio-like (leaf-like)

– Foliated equigranular crystalline texture

• Sedimentary– are rocks formed when fragments of plants, animals, or

rocks are compressed together or otherwise hardened; or they are masses of intergrown mineral crystals that precipitated from water( like the rock salt that remains when the ocean water is evaporated)

– Common Sedimentary Rock Textures– Clastic texture: contain clast (fragments) of minerals, other

rocks, plants, or animals– Detrital worn rock fragments

» Silty detrital (clastic) texture» Sandy detrital (clastic) texture» Layered crystalline texture» Coarse-grained detrital (clastic) texture

Metamorphic

• Green house effect– the property of the Earth’s atmosphere by which long-wavelength heat

radiation from Earth’s surface is trapped or reflected back by the atmosphere

• Earth’s climate system consists of 4 interacting subsystems– Atmosphere– hydrosphere– lithosphere– biosphere

• solar energy drives the system• some of the incoming radiation is reflected back into space from the clouds,

atmospheric pollutants, ice , snow and other reflective surfaces

• Tectonic movement affect – surface relief

• which influences atmosphere circulation – the geometry of continents and ocean basins

• which controls ocean circulations and location of ice sheets • while volcanic and industrial gasses affect atmospheric composition

– The Carbon Cycle• Natural fluxes of Carbon b/t the atmosphere, hydrosphere, biosphere, crust and

mantel– 1. carbon enters the atmosphere through volcanism, weathering and

biological respiration and decay of organic matter in soils– 2. photosynthesis incorporates carbon in the biosphere from which it can

become part of the crust if buried w/accumulating sediment• subduction liberates carbon from oceanic crust into the mantel• anthropogenic activities release carbon to the atmosphere through fossil fuel-fuel

use, combined w/deforestation and burning wood– The Greenhouse Gases

• some of the short-wave (visible solar) radiation reaching Earth is absorbed by the land and oceans, while some reflects back

• Earth also radiates long-wave radiation (infrared) back to space.• Greenhouse gases trap some of the outgoing long-radiation, causing the

atmosphere to heat up– W/inc. conc. Of these trace gases, the air temp of the lwr atmosphere rises.

• Historical Temperature Changes• - Hemispheric and global temp changes since the mid-nineteenth

century (w/both land and ocean data) • - long term trend is a rise of temp,• - interval being about 0.6 degrees C