ESCI 402 Earth History Exam 1

Physical geology

composition, structure, and geologic processes on Earth

Historical geology

focus on past events in Earth History

Primary source of information prior to 1500 CE?

The Bible

Earth’s Age

4\.6 Billion Years

How old we thought the world was prior to 1500 CE?

\~6000 years

Leonardo da Vinci

rejected Noah’s Flood origin for fossil deposits

Nicolaus Steno

created majority of the stratigraphic principles; organic origin and preservation fossils

James hutton

researched dynamic Earth cycles, geologic time, and uniformitarianism

William “Strata” Smith

researched biostratigraphy, geologic mapping, and the Principle of Faunal Succession

Charles Lyell

the Great Synthesizer; added two new stratigraphic principles: Principles of Cross-Cutting Relationships and Inclusions

Charles Darwin

found the theory of organic evolution

Inge Lehmann

discoverer of the Earth’s inner core

Principle of Superposition

in an undisturbed sequence of Strata, the youngest layer is at the top and the oldest layer is at the bottom

Principle of Original Horizontality

sedimentary layers are originally horizontal or parallel to the surface of accumulation

Principle of Original Lateral Continuity

sedimentary layers are originally laid down as laterally continuous sheets

Principle of Faunal Succession

sedimentary rocks are characterized by unique assemblages of fossils that change through time

Principle of Cross-Cutting Relationships

younger geologic features cut across older geologic features

Principle of Inclusions

a body of rocks is younger than any of it’s constituents

Walter’s Principle

the vertical succession of sedimentary lithologies corresponds to the original lateral distribution of those lithologies

Principle of Stratigraphy

rock formations defined by their distinctive lithologic and structured properties

S Waves

Secondary or shear waves; don’t pass through liquid

P Waves

Primary or compressional waves; can pass through liquid

Element

most fundamental substance into which matter can be separated by chemical means

Atom

smallest individual particle that retains all properties of a given element; made up of electrons, protons, and neutrons

Ion

atom with net positive or negative charge

Isotope

atom of the same element with different atomic masses

Mineral

any naturally occurring solid inorganic substance having a specific chemical composition and a characteristic crystal structure

Quartz

the most basic silicate with a chemical composition of SiO2; extremely resistant to weathering

Rock

any aggregate of mineral matter

Hydrosphere

water globe (mainly H, O)

Atmosphere

vapor globe (mainly N, O, Ar)

Biosphere

life globe (mainly H, C, N, O)

Lithosphere

rock globe (mainly H, O, Al, Si, P, Na, Mg)

Crust

outermost layer of the Earth’s chemical differentiation; composed of silicates; 10-70km thick

Mantle

second layer of the Earth’s chemical differentiation; denser/darker silicates; \~2800km thick

Core

inner most layer of the Earth’s chemical differentiation; iron and nickel; \~2500km thick

Lithosphere

first layer of the Earth’s physical differentiation; rigid; \~100km thick

Asthenosphere

second layer of the Earth’s physical differentiation; rocks are hotter, more ductile, and made mostly of plastic substances; \~100-300km thick

Mesosphere

third layer of the Earth’s physical differentiation; solid, denser; \~2600km thick

Outer Core

fourth layer of the Earth’s physical differentiation; liquid; \~2200km thick

Inner Core

fifth layer of the Earth’s physical differentiation; solid; \~1150km thick

Silicate minerals

primarily made with silicon and oxygen

Feldspar

group of aluminosilicates (Al, Si, O) that make up about 60% of the total weight of the crust

Mica

group of minerals that occurs as thin plates or sheets; includes muscovite (light), biotite (dark)

Pyroxene & Amphibole

silicates of Al, Ca, Mg, Fe; usually black to dark green colors

Olivine

silicates of Fe, Mg; olive green color

Garnet

aluminosilicates of Fe, Ca, Mg, Mn; red, brown, or yellow colors

Calcite & Aragonite

non-silicate minerals; composition of CaCO3; main constituent of limestone and marble; important biogenic minerals

Halite

non-silicate minerals; composition of NaCl; cleaves to form cubes

Gypsum

non-silicate minerals; soft, hydrous calcium sulfate; used in sculptures (alabaster variety)

Galena

non-silicate minerals; composition of PbS (lead sulfide); dense, metallic, cleaves into cubes

Igneous Rocks

rocks that form from crystallization of molten material (magma/lava)

Metamorphic Rocks

rocks that undergo a change in form due to the action of high heat, high pressure, or chemical alteration

Sedimentary Rocks

rocks that form from when sediment becomes compressed and cemented overtime

Foliation

layers within rocks

Porphyritic texture

has really coarse-grains embedded within fine-grains

Sialic

high-silica

Mafic

low-silica

Bowen’s reaction series

each mineral has a specific temperature of crystallization

Fractional Crystallization

the removal and segregation from a melt of mineral precipitates

What percent of the crust is made up of sedimentary rocks by volume?

5%

What percent of the Earth’s surface area is made up of sedimentary rocks?

75%

Transport

movement of sedimentary materials from point of weathering to point of deposition; occurs via wind, glacial transport, landslides, or running water

Chemical Weathering

decomposition/alteration of rocks and minerals by chemical means

Physical Weathering

processes that break rocks and minerals into smaller particles with no change in mineral/chemical composition

Deposition

settling or precipitation of sediments into layers (strata)

Clastic Sedimentary Rocks

composed of clasts (grains/particles) that are produced by physical weathering

Non-Clastic Sedimentary Rocks

sedimentary rocks formed by chemical or biological processes (ex. chert, rock salt, coal, chalk, or limestone)

Playa

flat desert valley

Fossils

any physical evidence of past life

Paleoecology

study of how past communities of organisms interacted with each other and with their environment

Paleogeography

plate tectonics

Taphonomy

the study of all that happened to organisms from the moment of death to the eventual preservation as a fossil

Unaltered remains

original material is preserved; most commonly hard parts (teeth, bones, shells)

Altered remains

original material has been chemically or physically changed

Replacement

original material has been chemically or physically altered (ex. pyrite, silica)

Permineralization

pores or vessels are filled in with a new mineral, usually by crystallization or precipitation of minerals out of solution

Carbonization

carbon film is the only remaining part of original organic material

Indirect remains

provide evidence for presence and/or activity of past life

Molds

body impressions

Cast

internal molds

Trace fossils

tracks, burrows, dwellings, coprolites (feces)

Plate Tectonic Theory

Earth’s lithosphere is broken into rigid plates that are moving over a deformable/ductile asthenosphere

Alfred Wegener

developed the idea of continental drift; thought lighter continents plowed through denser oceanic crust, but this was debunked

Paleomagnetism

Earth’s magnetic field has changed in the past, but geomagnetic poles have flipped; but geomagnetic poles have always been close to Earth’s rotational pole

Seafloor spreading

creation of near oceanic crust mid-ocean ridges

Subduction zones

also known as Wadati-Benioff zones, when two converging plates cause an uplift of one and a subduction of another

Volcanic chains

occurs due to melting of a downgoing plate slab

What forces drive plate motion?

thermal convection in the mantle; ridge-push and slab-pull; thermal mantle plumes (hotspots)

Sedimentary facies

characteristics of a rock that indicate its depositional environment

Stress

force applied per unit area (ex. compressional, tensional, shear)

Strain

deformation due to stress (ex. elastic, brittle, ductile)

Strike

compass direction of a line formed by the intersection of a rock layer and the horizontal plane

Dip

angle of inclined plane with respect to horizontal

Anticline

upwardly folded rocks

Syncline

downwardly folded rocks

Monocline

slanted fold in the rocks

Dome

circular upwardly fold in the rocks

Basin

circular downwardly fold in the rocks

Plunging folds

tilted fold in the rocks