1st Semester Exam Earth Science

Geology

a science that deals with the history of the earth as recorded in rocks

Contact Metamorphism

a change in the texture, structure, or chemical composition of a rock due to contact with magma.

foliation

The metamorphic rock texture in which mineral grains are arranged in planes or bands.

crystallization

The process by which atoms are arranged to form a material with a crystal structure

Magma

hot melted rock material, molten rock beneath the earth's surface

Decay Rates

The rate at which a radioactive isotope disintegrates until a final non-radioactive isotope is formed.

solidification

the rock cycle process of becoming hard or solid by cooling Ex: magma into an igneous rock

grain size

the size of the grains that make up a rock, which helps to classify the type of rock

Carbon 14

radioactive isotope of carbon, with 6 protons and 8 neutrons, its presence in organic materials is the basis for using radioactive dating

mafic

describes magma or igneous rock that is rich in magnesium and iron and that is generally dark in color

felsic

Describes magma or igneous rock that is rich in feldspars and silica and that is generally light in color.

Biosphere

the regions of the surface and atmosphere of the Earth (or other planet) where living organisms exist

Continental Drift

the gradual movement and formation of continents as described by plate tectonics

Density

the amount per unit size, the amount of mass in a given volume

index fossils

distinctive fossil used to compare the relative ages of fossils

igneous rock

produced under conditions involving intense heat, rock formed by the solidification of molten magma or lava

Weathering

The breaking down of rocks and other materials on the Earth's surface.

sedimentary rock

A type of rock that forms when particles, sediment, from other rocks or the remains of plants and animals are pressed and cemented together.

geologic time scale

the time of the physical formation and development of the earth (especially prior to human history), a record of the geologic events and life forms in earth's history

Regional Metamorphism

Metamorphism caused by high pressures and temperatures that extend over large regions, as happens where plates collide.

Metamorphic rock

Rocks changed by intense heat or extreme pressure

Metamorphism

change in the structure of rock by natural agencies such as pressure or heat of introduction of new chemical substances

Law of Superposition

The geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it.

Radioactive Substance

a substance that emits ionizing radiation; also called a radionuclide or radioisotope

Plate Boundaries

At plate boundaries, Earth's crust is broken (fault) and rocks slip past each other in one of 3 types of plate boundaries.

Plate Collision

continental and/or ocianic plates running into each other

Atmosphere

the mass of air surrounding the Earth

Chemical Sedimentary Rock

sedimentary rock that forms when minerals precipitate from a solution, like when water evaporates and leaves mineral deposits. (Ex: Salt Lake).

Strata

layers of sedimentary rock

Organic Sedimentary Rock

Sedimentary rock that forms from the remains of plants or animals. (Coal, Fossiliferous Limestone)

Clastic Sedimentary Rock

Sedimentary rock that forms when fragments of preexisting rocks are compacted or cemented together. (Sandstone, Pudding Stone, Siltstone)

Rock Cycle

the series of processes in which rock forms, changes from one type to another, is destroyed, and forms again by geological processes.

Nonfoliated

the texture of metamorphic rock in which the mineral grains are not arranged in planes or bands

Lithification

The process that converts sediments into solid rock by compaction or cementation.

Stratification

the process in which sedimentary rocks are arranged in layers

Isotope

one of two or more atoms with the same atomic number but with different numbers of neutrons

Absolute dating

any method of measuring the age of an event or object in years.

Relative dating

any method of determining whether an event or object is older or younger than other events or objects

Daughter and Parent Ratio

Radioactive parent material decays into stable daughter material and ratios help determine half life.

Pleistocene ice age

fairly recent geological period when huge ice sheets covered most of North America and other continents

Original Horizontallity

sediments originally were deposited in horizontal layers

Half-life

length of time required for half of the radioactive atoms in a sample to decay

Permian extinctions

a mass extinction that claimed 96% of marine animal species and 8 out of 27 orders of insects and thought to have caused by enormous volcanic eruptions

Petrification

a process in which an organism's tissues are completely replaced by minerals

Crinoids, Brachiopods, Petoskey stones

Common Michigan fossil from the Devonian Period.

Permineralization

The process by which minerals replace parts of an organism.

Uranium 238

The radioactive isotope of uranium having an atomic mass of 238 and a half-life of 4.5 billion years. Decays into Lead.

Unconformities

a break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.

Radiometric dating

a method of determining the absolute age of an object by comparing the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope

K-T Boundary

layer of iridium that is found over the entire planet, between Cretaceous and Tertiary Rock, that is believed to be evidence for a meteor impact around the time of the mass ext. of the dinosaurs.

Cross-cutting relationships

principle stating that a fault or intrusion is younger than the rock it cuts across

Plate tectonics

the theory that the Earth's lithosphere is divided into tectonic plates that move around on top of the asthenosphere, driven by convection currents.

Mesosphere

The strong, lower part of the mantle between the asthenosphere and the outer core

Asthenosphere

the soft layer of the mantle on which the lithosphere floats

Rock

A naturally occurring solid mixture of one or more minerals or organic matter

Convergent boundary

a plate boundary where two plates move toward each other

Transform boundary

a plate boundary where two plates move past each other in opposite directions

Divergent boundary

a plate boundary where two plates move away from each other

Sea floor spreading

when two oceanic plates pull apart, magma rises and new crust is formed

Continental drift

the hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations and continue to drift today

Continental crust

The thickest type of crust., The portion of the earth's crust that primarily contains granite, is less dense than oceanic crust, and is 30-100 km thick

Oceanic crust

the portion of Earth's crust that is usually below the oceans, thinner and higher in density that continental crust and basaltic composition

Convection currents

tectonic plates are moved around by these currents in the asthenosphere. There may also be convection in the liquid outer core.

Subduction zone

The region where oceanic plates sink down into the asthenosphere.

Mid-Ocean Ridge

an undersea mountain chain where new ocean floor is produced; a divergent plate boundary

Outer core

a layer of molten iron and nickel that surrounds the inner core of Earth

Inner core

a dense sphere of solid iron and nickel at the center of Earth

Upper mantle

Layer of the earth below the Earth's crust and with the crust forms the lithosphere

Lithosphere

the solid part of the earth consisting of the crust and outer mantle; the tectonic plates

GPS

A system that determines the precise position of something on Earth through a series of satellites, tracking stations, and recievers. Global Positioning System.

Pangaea

(plate tectonics) a hypothetical continent including all the landmass of the earth prior to the Triassic period when it split into Laurasia and Gondwanaland

Hot spot volcano

A volcano that forms when a tectonic plate moves slowly over an area of hot magma that pushes up through the crust. Can form a chain of islands.

Tectonic Plate

a piece of the lithosphere that moves around on top of the asthenosphere; there are 10 major tectonic plates

lava

magma that reaches Earth's surface

Heat and pressure

Two processes that form metamorphic rocks (in alphabetical order).

Cementing and compaction

Two processes that form sedimentary rock

Ridge push

when the force of gravity moves a plate downward and away from a ridge; sea-floor spreading

Slab pull

a mechanism that contributes to plate motion in which cool, dense oceanic crust sinks into the mantle and "pulls" the trailing lithosphere along; convergent boundary

Cooling

Magma cools into Igneous rock

Extrusive

rocks that form from magma above the surface

Intrusive

rocks that form from magma below the surface

Deposition

the process of dropping, or depositing, sediment in a new location

Erosion

the wearing away of soil and rock particles by waves, wind, running water, or glaciers

Geologic Time

the succession of eras, periods, and epochs

Radioactive decay

The rate of decay of radioactive substances such as carbon 14 or uranium is measured in terms of their half-life

Mountain ranges

formed when two continental plates converge and neither is denser than the other so no subduction occurs