Geology Study Guide: Ch 7, 8, 9, & 15

Relative dating

is the process of determining if one rock or geologic event is older or younger than another, without knowing their specific ages

○ Stratigraphy

the study of rock layer and their relationships to each other within a specific area.

○ Superposition

in an undisturbed sequence of strata, the rocks on the bottom are older than the rocks on top

○ Original horizontality

layered rocks are generally laid down flat at their formation

○ Lateral continuity

layered rocks can be assumed to continue if interrupted within its area of deposition

○ Cross cutting relationships

a geological object can not be altered until it exists, meaning, the change to the object must be younger than the object itself

○ Inclusions

when one rock formation contains pieces or inclusions of another rock, the included rock is older than the host rock

○ Fossil succession

fossils that correlate to the units of geologic time scale. A

Absolute dating

is quantitate method of dating a geological substance to a specific amount of time in the past

○ Radioactive decay

unstable isotopes spontaneously decay over time releasing subatomic particles or energy. When this occurs, an unstable isotope becomes a more stable isotope of another element.

○ Half-life

the calculated amount of time that half of the mass of an original (parent) radioactive isotope breaks down into a new (daughter) isotope

What is the Rp, Sd, and ratio for 1 half-life

50 50 1:1

What is the Rp, Sd, and ratio for 2 half-life

25 75 1:3

What is the Rp, Sd, and ratio for 3 half-life

12.5 87.5 1:7

What is the Rp, Sd, and ratio for 4 half-life

6.25 93.75 1:15

Angular Unconformity

where sedimentary strata are deposited on a terrain developed on sedimentary strata that have been deformed by tilting, folding, and/or faulting. So that they are no longer horizontal

Disconformity

where is a break or stratigraphic absence between strata in an otherwise parallel sequence of strata

Nonconformity

where sedimentary strata are deposited on crystalline (igneous or metamorphic) rocks.

Earth’s primitive atmosphere

which consisted mainly of H2O vapor and CO2, formed by outgassing. Gases trapped in the planet’s interior are released by volcanic eruptions

200,000 years ago

Human voice box evolves and we can speak coherent words. Allows us to communicate with other humans and information can be shared between individuals

7 mil years ago

Large abundance and forming of grass
Evolved to walking on two legs, standing on two feet, allowed us the use of our hands

2.6 mil years ago

Stone age - Hominids began to break rocks to build hammers with a cutting edge
Started to consume more calories which led to bigger brains

Paleozoic - 541 - 251.9 mil. years

Early shelled organisms, primitive fish
First land plants, forests (evergreens), amphibians
First reptiles, abundance of sharks, coal-forming swamps

Mesozoic 251.9 - 66 mil. years

Flying reptiles, first dinosaurs; first mammals
Dinosaurs diverse and abundant, earth flowering plants, placental mammals

Big Bang

This provided the elements, along with material from former stars, to form the solar system. As material collected, high velocity impacts of matter, called planetesimals, caused Earth’s temperature to increase

Hydrogen

the element that makes up everything

Moon

keeps Earth steady and tilted on its axis. Makes seasons and stable climate

Stress

force applied to an object, typically dealing with forces within the Earth

Tensional

stresses that pull objects apart into a larger surface area or volume; stretching forces. Divergent plate boundary
Resulting strain: Plastic - stretching and thinning
Fault type: normal

Compression

stresses that push objects together into a smaller surface area or volume; contracting forces. Convergent plate boundary
Resulting strain: Elastic - shortening and thickening
Fault type: reverse

Shear

stress within an object that causes a side-to-side movement within an internal fabric or weakness. Transform fault boundary
Resulting strain: Brittle - tearing
Fault type: strike-slip

Deformation

A strain that occurs in a substance in which the item changes shape due to a stress.

Elastic deformation

is strain that is reversible after a stress is released.

Ductile deformation

A bending, squishing, or stretching style of deformation where an object changes shape smoothly.
Occurs when enough stress is applied to a material that the changes in its shape are permanent, and the material is no longer able to revert to its original shape.

Folding

layers of rock that are curved or bend by ductile deformation

Axial planes

dividing two - dimentional line between the two sides of a fold

fold axis

the line along which the bending occurs and is where the axial plane intersects the folded strata

symmetrical folds

have a verticle axial plane and limbs ahve equal but opposite dips

asymmetrical folds

have dipping, non-vertical axial planes, where the limbs dip at different angles

anticline

A-shaped folds that are convex-upward in shape
the oldest rock strata in the center, younger on the outside

Synclines

Trough-like, or U shaped, folds that are concave-upward in shape. They have beds that dip down and in toward the central fold axis. Older rock is on the outside of the fold and the youngest rock is inside of the fold axis.

Normal faults

move by a vertical motion where the hanging-wall moves downward relative to the footwall along the dip of the fault. are created by tensional forces in the crust. occur at divergent plate boundaries, where the crust is being stretched by tensional stresses

Reverse faults

compressional forces cause the hanging wall to move up relative to the footwall. Thrust faults carry older rocks on top of younger rocks and can even cause repetition of rock units in the stratigraphic record. Convergent plate boundaries with subduction zones

Strike-slip faults

have side-to-side motion. are most commonly associated with transform plate boundaries and are prevalent in transform fracture zones along mid-ocean ridges. Fault blocks on either side of the fault do not move up or down relative to each other, rather move laterally, side to side. Is determined by an observer standing on a block on one side of the fault.

Earthquakes

are felt at the surface of the Earth when energy is released by blocks of rock sliding past each other, i.e. faulting has occurred. Occur along active plate boundaries. Intraplate earthquakes (not along plate boundaries) occur and are still poorly understood. Body waves include primary (P) waves and secondary (S) waves.

P waves

Are the fastest body waves and move through rock via compression, very much like sound waves move through air. Rock particles move forward and back during passage enabling them to travel through solids, liquids, plasma, and gases.

S waves

travel slower, following P waves, and propagate as shear waves that move rock particles from side to side. Because they are restricted to lateral movement, can only travel through solids but not liquids, plasma, or gases.

Surface waves

Are produced when body waves from the focus strike the Earth's surface. Surface waves travel along the Earth's surface, radiating outward from the epicenter. take the form of rolling waves called Raleigh Waves and side to side waves called Love Waves

Raleigh Waves

Surface waves that have a up and down motion

Love waves

Surface waves that have a side-to-side motion

Wave arrival times recorded on seismographs at multiple stations

seismologists can apply triangulation to pin point the location of the epicenter of an earthquake.

By comparing data from multiple seismographs

scientists can map the properties of the inside of the Earth, detect detonations of large explosive devices, and predict tsunamis.

Shaking

is more severe closer to the epicenter. The severity of shaking is influenced by the location of the observer relative to epicenter. direction of rupture propagation and path of greatest rupture.

Climate

long term averages and variations within the conditions of the atmosphere. Defined using Koeppen System. Uses monthly average temperature and precipitation associated with different types of vegetation

Weather

current conditions within the atmosphere

The gasses that are part of the Earth

which are mainly nitrogen and oxygen - 78% nitrogen - 21% oxygen - 1% argon

Troposphere

Permanent gasses. Gasses whose proportions stay constant

Greenhouse effect

Gases that are responsible for warming and cooling the planet. Is a natural and necessary process. Earth would be 33 degreases colder without it. All surface water would be frozen. Little life would exist. Natural effect is from water vapor.

Milankovitch cycles

Natural changes in Earth’s Orbit

The causes of long-term climate changes

Changes in ocean`s circulation. The slow movement of the continents. Variations in the shape of Earth`s orbit. Changes in the angle of Earth's tilt (the range of temperatures throughout the year)

The theory of Anthropogenic Climate Change

humans are causing most of the current climate changes by burning fossil fuels such as coal