GEOL 102 Exam 1 GMU

Physical geology vs. Historical geology

Physical geology deals with materials and processes that make up the Earth, Historical geology is applying chronology to events in Earth's past

Relative age

Determination that something is younger or older than something else

Absolute Age

Precise measurement of how much time has passed since something was created or modified

Fossils

Remains, traces, or other indications of life

Principal of Original Horizontality

Sediment is deposited in layers that are originally horizontal

Principle of Original Lateral Continuity

Rock layers extend in all directions until they thin out, encounter a barrier, or grade laterally into another rock type

Concept of Uniformitarianism

The present is the key to understanding the past. Past history of Earth must be explained by what is happening now

Principle of Actualism

Natural laws do not change with time

Concept of Catastrophism

History of life on Earth is marked by catastrophes. Each calamity extinguishes all life on earth and new animals and plants appear after

Principal of Natural Selection

Species evolve over time and the most favorable traits pass on to the next generation and the rest die off.

What are the Eon divisions in the Geologic TimeScale

Phanerzoic (541 Ma), Proterozoic (0.541 - 2.5 Ga) , Archean (2.5 Ga - 4.0 Ga) , Hadean(4.0 Ga - 4.6 Ga): Youngest to Oldest

Principle of Superposition

in undisturbed layers of rock, the oldest rocks are on the bottom and the rocks become progressively younger toward the top

Principle of Cross-Cutting

younger features cut across older features in rock strata

How can radioactive materials be used to determine the ages of geologic samples?

Radiometric dating uses the decay of specific element isotopes to determine the absolute age of a rock

What is half-life?

The time required for half of a given amount of an unstable parent to decay to a daughter isotope/element. It is nonlinear.

What are the requirements for a material to be a mineral?

Occurs naturally as an inorganic solid/Has specific internal structure/Has specific chemical composition

How are minerals defined?

Based on their properties and chemical composition.

What are some tests you can do to identify a mineral?

Microscopic analysis or a field test kit(Physical properties) that check color, streak, luster, cleavage, fracture, hardness, crystal shape.

Silicate minerals

Silicate minerals contain silicon(Si) and Oxygen(O) and bind together in the shape of a tetrahedron

Non-silicate minerals

Carbonates, sulfates, sulfides, chlorides, oxides

What are the requirements for a material to be a rock?

Rock is a solid material that occurs naturally and is composed of one or more minerals/organic material

How are igneous rocks formed?

Form from solidification of molten rock(magma or lava)/ melting of a rock

Do all minerals in igneous rocks crystalize at the same time?

No minerals crystallize from cooling magma in a systematic sequence

Intrusive vs. Extrusive Igneous Rocks

Intrusive solidifies underground and Extrusive solidify on the surface where they cool much faster and become fine-grained

What are the differences between felsic and magic magmas?

Felsic has more silica and less magnesium and iron and more viscous magma(Does not flow to the surface easily)

Viscosity

The state of being thick, sticky, and semifluid in consistency, due to internal friction

How are sedimentary rocks formed?

Formed from sediments that have been consolidated from compaction, cementation, or crystallization.

Formation process of sedimentary rocks involves

Weathering, Erosion/Transportation , Deposition, Lithification

How are metamorphic rocks formed?

Rocks that have been altered by heat or pressure, but not melted

Geologic Time Scale divisions

Eon → Era→Period→Epoch→Age

Metamorphic grade

the degree to which the parent rock changes during metamorphism

Folatiated vs Non-Foliated metamorphic rocks

Foliated rocks have parallel alignment of crystals or grains(planar orientation) and non-foliated are created when the stress on the rock is uniform or the crystals do not deform

What does well sorted mean in the context of sediments?

The grains are all the same size and it was most likely transported by wind or water

What does the shape of sediment grains tell you?

The farther sediments are transported, the rounder they become. They are angular if they haven't been transported far.

Why are some ripples in sediments symmetrical and some asymmetrical?

Symmetrical ripples are created when currents come from both sides or there is erosion on both sides of each structure.

What does cross-bedding in sandstone tell you about the formation mechanism?

Sediments were deposited as ripples or dunes

What is limestone made of?

Carbonates

What is the difference between bio-clastic and non-clastic limestone?

Most limestones are bio-clastic because they contain fossils but some are formed without biologic activity

Where are most limestones formed?

Marine environments

Stratigraphy

study of stratified rocks, especially their geometric relations, compositions, origins, and age relations

What environmental conditions are most favorable for fossil preservation?

High deposition zones, Shallow sea, Low oxygen environments for organic material

Fossils are usually found

In sedimentary rocks

What physical traits or properties of organisms are most favorable for fossil preservation?

Hard body parts(Shells, bones)

How do fossils help with dating sedimentary rocks?

Some fossils were only around for a short period of time in the geologic time scale and if found inside a rock, it can be dated to that fossils short time period

Index fossil

a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found

Principle of Fossil Succession

Fossil organisms succeed one another in a definite and determinable order, and any time period can be recognized by its fossil content.

How do fossils provide a record of the past environments?

Certain fossils can only be found in certain environments, so it shows how the environment has changed

What is meant by the Taxonomy of Life

The systematic naming and growing of organisms on Earth that is not absolute and can change

What level of Taxonomy marks the level of breeding between members

Species

How is Taxonomy classified

By observable traits

How do variations occur within a population?

Variations occur naturally through reproduction and mutations in genes

How do the traits of the population as a whole evolve?

The population as a whole evolves when the population without the favorable trait dies off

What is the evidence of evolution from paleontology?

Horse teeth have evolved be specialized from eating leaves to eating grass horse fossils have teeth that are more flat

What is the evidence of evolution from biology?

Similar structure of body parts in different modern day organisms/Useless organic structures/Humans having similar genome to chimpanzees

What are the major divisions of the Earth's interior?

Crust → Mantle → Core

2 Divisions of Earth based off of properties

Lithosphere(Hard outer shell of earth) → Asthenosphere(Soft, weak steel of upper mantle)

Seismic wave

Vibrations that travel through Earth carrying the energy released during an earthquake or artificially

Types of body waves

P(Primary) waves and S(Secondary) waves

P-wave

Compressional(push-pull) wave that can travel through all materials

S-wave

Shear wave(Oscillation movement) that can only travel through solids

How can P and S waves be used to understand the Earth's interior

P waves can travel through the core and S waves can't therefore there exists liquid in Earths core

What is a lithospheric plate?

Different sections of the lithosphere that move around on the asthenosphere

What does the movement of lithospheric plates say about the continent locations in the past?

The continents were once connect

What are the ways the lithospheric plates can move in respect to each other?

Converge(Against Each other)/Diverge(Away from each other)/Transform(Slide past each other

What is a fault?

A fracture in a rock along which motion has occurred

Types of faults

Normal(Hanging wall falls), Reverse(Hanging wall rises), Strike-slip(Lateral walls slide past each other)

What is a fold?

A bend in layers of rock created by compression

Types of folds

Anticline, syncline, dome, basin, monocline

Anticline

Oldest rocks in center

Syncline

Youngest rocks in center

Basin

Downfolded circular features with youngest strata in center

Dome

Upfolded or arched features with oldest strata in the center

What are some of the lines of evidence that support Plate Tectonics Theory?

Earthquakes occur along plate borders/Volcanoes located on pacific rim/Wandering of magnetic poles/Crust age correlate with distance from mid-ocean ridge

Types of Surface Waves

Rayleigh- up down

Love waves- side by side(cause earthquakes)

Surface waves vs Body waves

Surface waves can only move on the surface while body waves travel through the interior of Earth