Geology 1403 Exam 3 Blinn Bockoven

Age of the Earth

4.5 Billion Years

Precambrian

- 3 eons
- 88% of Earths History
- 1st 4 Billion years
- Earliest record of life (Bacterial Stromatolites)

Paleozoic Era

- 250 MYA "Age of Trilubites
- Mass extinction
- 1st Fish then reptiles
- 90% of Ancient life was wiped out

Mesozoic Era

- 65 MYA "Age of Dinosaurs"
- Mass extinction by volcanic eruption

Cenozoic Era

- Present Time "Age of Mammals"
- First hominids

Present Time

Phonerozoic Eon - Cenozoic Era - Quaternary Period -

Unconformities

Surface that represents periods of erosion or non deposition

Angular Unconformities

Erosion surface between two bodies of layered sedimentary rock that are not parallel
- Ex. Huttons unconformity Siccor Point, Scotland

Nonconformities

Erosional surface between older metamorphic or igneous rock and younger sedimentary layers or lava flows
-Ex. The Grand Canyon, AZ

Disconformity

Parallel sedimentary rock layers or lava flows with a missing rock layer
- Representing erosion or non deposition

Identify Disconformity

- Missing fossils
- Radiometric dating
- Comparison to other Stratigraphic sections

Relative Dating

Sequencing events
(Related to all Laws, Index Fossils, & Fossil Assembledge)

Law of Original Horizontality

Sedimentary rocks originally deposited horizontally

Sedimentary rocks usually deposit in?

Water

Law of Superposition

Oldest sedimentary rocks at the bottom and youngest at the top

Law of Lateral Continuity

Sedimentary rock beds can be traced laterally for long distances

Law of Cross-cutting Relations

A feature that cut through a rock must be younger than the rock that it cut through
- Ex. Intrusive igneous rock, Dikes, Stills, and Faults

Law of Inclusions

Any piece of rock that has become involved in another rock must be older than the rock into which it has been incorporated
- Ex. Foreign rock inclusion = Xenolith

Law of Faunal Succession

Fossils succeed one another in a definite and determinable order and therefore any time period can be recognized by its fossil content

How to see evolution through time?

Fossil Documents

Index Fossils

Are geographically wide spreed but limited to a short span of geological time

Fossil Assembledge

Dileneaten a shorter span of geological time and may indicate the environment of deposition

Radiometric Dating

- Based on the radiometric decay of unstable isotopes
- The rate of decay of these elements is a known calis
- Numerical dating, Absolute dating, Isotopic dating

Isotopes

Are atoms with different numbers of neutrons, an element can have more than one isotope

Parent Isotiopes

Unstable isotopes - Decays to a Daughter isotope

Daughter Isotope

Stable isotope product with an exponential rate of decay

Half-Life (T 1/2)

The time it takes for 1/2 of the isotope to decay to its product is a known constant rate of decay for each Parent-Daughter

1 Half Life

P (50%) - D (50%)

2 Half Lifes

P (25%) - D (75%)

3 Half Lifes

P (12.5%) - D (87.5%)

Anticline

- Outward dips and oldest beds in the middle of the fold
- Bed dips towards center
- Formed by compression
- "Frown" "Arch" shaped

Syncline

- Inward dips and youngest beds in the middle
- Bed dips aways from center
- Formed by compression
- "Smile" ("U" - shaped)

Plunging Anticline

- Plunge through "their nose" oldest rock is in the center
- Beds dip away from the hinge line

Plunging Syncline

- Plunge through "open end" of fold youngest rock is in the center
- Beds dip towards the hinge line

Dome

- Circular outcrops
- Outward dips and oldest beds in the middle
- Beds dip away from center
- Ex. Block Hill, SD

Basin

- Downwarping
- Youngest rock in the in the center
- Beds dip towards center

Normal Fault

- Tension
- Dip/Slip fault
- Lengthening of crust
- Footwall moves up / Hanging wall moves down
- "miss" a bed as you drill down

Reverse Fault

- Compression
- Shortening of crust
- Footwall moves down / Hanging wall moves up
- "repeat" a bed as you drill up

Right Lateral Strike-Slip Fault

- Horizontal movement
- Shear stress

Left Lateral Strike-Slip Fault

- The fault is left or right depending on which way the rock has moved when you look at it (while standing on either side"

Stress

Force that deforms rocks

Deformation / Strain

- Changes that occurs in rocks

Brittle

Fracturing

Ductile

Bending

Elastic

Rubber band

Rock Strength Depends on?

- Temp
- Pressure
- Rock type
- Time

Igneous and Metamorphic Rocks

Brittle

Sedimentary Rocks

- Ductile
- Weak rocks flow
- Strong rocks break

Outcrop

Bedrock exposed at the earths surface

Strike

Compass direction created by the intersection of a dipping bed at a horizontal surface (Strike line is parallel to contact line)

Dip

The angle at which a rock layer is inclined from the horizontal (always perpendicular to the strike)

Monocline

A stair step fold, often draped over a deep basement fault

Joint

Fracture in earths surface with NO movement

Fault

Fracture in earths surface with movement

Continental Drift

Proposed by Alfred Wagner in the early 1900s he believed all continents were merged together into a supercontinent called "Pangea" during the late Paleozoic continents began to drift during early Mesozoic

Paleomagnetism

First magnetic field N-S Dipolor BarMagnetForm by ironing the Earth's core
(Early evidence after World War II)

Seafloor Spreading

- Support to the continental drift and provided a mechanism
- Occurs through the upwelling of magma at mid ocean ridges and is subsequent outward movement on either side

Lithosphere

Forms of solid/rigid tectonic plates that are composed of the crust

Asthenosphere

Forms a solid book plastic layer in the mantle upon which the tectonic plates glide

Driving Mechanisms of Plate Tectonics

- 1) mantle convection - heat rises/cold sinks - heat from formation of earth - heat loss from core - radioactivedecay

Average Rate of Plate Movement

5cm a year

Divergent Plate Boundry

- Tension
- Moving away from eachother
- Crust created
- Normal Fault

Decompression Melting

How magma is generated at the mid ocean ridges/rises

Hydrothermal Vents

Black Smokers

Oceanic Ridges/Rises

- 70km undersea Mts ranges 2-3km wide
- Rift Valley and Center/sea floor spreading center

Rifts

Newly forming divergent plate boundaries on the continent called continental rifting

Convergent Plate Boundry

Compression, plates moving towards each other crust destroyed normal fault

Subduction

Zone where the denser oceanic plates sinks beneath a less dense oceanic or continental plate

Flux Melting

- Occurs when water is dragged down with the subducting plate
- Water lowers the rocks melting temp so the magma forms at about 100km

Volcanic Island Arc

Occur at the ocean- ocean convergent where one oceanic plates of subducts under the other and flux melting forms a chain of volcanic islands called a volcanic island Arc

Continental Volcanic Arch

Forms when oceanic crust subducts beneath continental crust on an adjacent plate creating an arc shaped mountain though

Trench

- Formed by seduction, convergent plate boundary
- Very deep elongated cavity bordering a continental or An Island arc

Ring of Fire

String of volcanoes and sides of seismic activity or earthquakes around the edge of the Pacific ocean (Most earthquakes occur here)

Ocean-Ocean Convergents

One oceanic plates of dogs under the other oceanic plate

Ocean-Continent Convergents

Magma is created at about 100km depth by flux melting because water is dragged down with the oceanic plate

Continent-Continent Convergents

Too low density fell sick continental plates collide neither subduct

Transform Plate Boundry

Sheer stress, plates move side-by-side crust conserved, strikes slip fault

San Andres Fault

Famous example on land, right lateral strike slip fault at transform plate boundary

Intreplate Mantel Plume "Hot Spots"

- Upwelling mantle plan, decompression melting
- Chain of volcanoes form as plate moves over stationary mantle plume hotspot

Evidence of Plate Tectonics

1) Ocean drilling- youngest assault at mid Ocean Ridge basalts get older away from mid Ocean Ridge
2) Hotspot tracks
3) Paleomagnetism Phone via iron
4) Apparent polar wondering
5) GPS

Young Mts

High jagged rocks

Old Mtns

Low gentle peaks

Highest Elevation Mtn in the World

Mount Everest

Highest Elevation Mtn in the USA

Mount Mikini

Isostacy

Principle that states that low density continents crust "floats" On more dense mental rocks

Tension / Normal Faulting

- Divergent plate boundrys
- Broad uplifting causes tension foulting
- Mantle upwelling causes doming of the crust and normal faulting

Oceanic Ridges

- Mid Atlantic Ridge, East Pacific rise
- Underwater mountain chains associated with normal faulting
- Rift Valley and center = graben

Horst

Ranges

Grabens

Basins

Fault Block Mtns

Normal faulting
- Ex. Grand tetons WY

Compression

- most mountains formed Compression force at convergent plate boundaries

Thrust Faulting

Trust falls are common at consonant - Content convergence

What covers 70% of the earths surface

Water

Guyots

Flattops seamount by wave erosion

Seamount

More than 1 million, most below sea level, most common specific, some form of her hotspots

James Hutton

Founder of modern geology

Charles Darwin

Theory of evolution (natural selection)

Darwins Theory of Coral Reef Formation

1) Fringing Reef
2) Barrier Reef
3) Atoll

Alfred Wegenor

Theory of Continental Prift

Mid ocean Ridges

Or a convergent form by flux melting