GEO EXAM 2 Study Guide PDF

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Study guide for the second geology exam....

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GEOLOGY EXAM 2 Rock Deformation - Chapter 8 8.1 How Do Rocks Respond to Stress? ● Force ● Stress ○ Force per area ● Differential stress → different amounts of stresses from different directions ● Confining pressure → same amount of force from each direction ● Displacement, Rotation, & Strain

8.2 How Do Rocks Respond to Changes in Stress, Temperature, and Fluids? ● How rocks respond depends on … ○ The type and magnitude of stress, the pressure and temperature conditions, & the amount of fluid present in the rock ● Three types of differential stress: ○ Compression, tension or shear ● Shallow → Brittle ● Deeper → Ductile

8.3 How Do Rocks Fracture? ● Two main types of fractures: ○ Joints → crack where rock pulled apart ■ Stresses that form joints: burial and tectonic forces, cooling and contraction, & unloading ○ Faults → rocks have slipped past one another ■ Most form when horizontal or vertical compressive stress exceeds the rock’s strength

● Vertical Joints

○ Form when the stress field allows the rock to be pulled apart in a horizontal direction ● Horizontal Joints ○ Form if a rock is pulled apart in a vertical direction

8.4 What Are Different Types of Faults? ● Dip-Slip Fault ○ Slip along a fault can be parallel to the dip - one block moves up or down relative to the other block

● Strike-Slip Fault ○ Slip along a fault can occur in a horizontal direction, parallel to the strike

● Oblique-Slip Fault ○ Slip along a fault can also occur in a direction that is oblique, being parallel to neither the dip nor the strike

● Hanging wall and Footwall:

● Three main types of faults: ○ Normal Fault ■ Hanging wall moves down relative to the footwall ○ Reverse Fault ■ Hanging wall moves up relative to the footwall ○ Strike-Slip Fault ■ Rocks move along a fault with a side-to-side motion, parallel to the strike of the fault surface ● Relative Displacement of Fault Blocks: ○ Graben → can refer to the down-dropped block or the resulting valley ○ Horst → a block that is uplifted relative to blocks on either side

8.5 What Are Folds and How Are They Shaped? ●

Anticline ○ Rock layers warp up in the shape of an A ○ Oldest rocks in the center of the fold

● Syncline ○ Rocks fold down in the shape of a V or U ○ Youngest rocks in the center of the fold ● *Anticlines and synclines occur together - usually as a part of series of folds ● Dome ○ Layers that are uplifted in a circular or elliptical area and dip away in all directions

● Basin ○ Opposite of a dome -- layers dip toward the center of the basin from all directions

● Monocline → in some folds, nearly flat layers bend down (dip) in one direction and then flatten out again https://quizlet.com/97501426/geo-chapter-8-deformation-and-metamorphism-flash-cards/

Geotime - Chapter 9 9.1 How Do We Infer the Relative Ages of Events? ● Five Main Principles of Relative Dating: ○ 1) Most Sediments are Deposited in Horizontal Layers ■ Original horizontality ○ 2) A Younger Sedimentary or Volcanic Unit Is Deposited on Top of Older Units ■ Principle of superposition ○ 3) A Younger Sediment or Rock Can Contain Pieces of an Older Rock ■ inclusions/clasts = older ○ 4) A Younger Rock or Feature Can Cut Across Any Older Rock or Feature ■ Cross-cutting relations ○ 5) Younger Rocks and Features Can Cause Changes Along Their Contacts with Older Rocks ■ Contact effects → indicate that the magma is younger than the rocks that were altered

9.2 How Do We Study the Age of Landscapes? ● A landscape surface is older than any rock that is deposited on top of the surface ● Sometimes can’t be dated directly, but we can infer its age relative to other features

9.3 What Is the Significance of an Unconformity? ● Unconformity → something is missing in the rock record. There are three types: ○ Disconformity ■ If rock layers are not tilted before they are overlapped by younger layers, but the boundary still represents millions of years of time ■ Parallel to rock layers ○ Nonconformity

■ When some erosion surfaces form on top of rocks that are not layered, especially igneous rocks like granite ○ Angular Unconformity ■ Underlying rocks are tilted before formation of the erosion surface

9.4 How Are Ages Assigned to Rocks and Events? ● Isotopic dating → determining the ages of rocks using analytical measurements ● *half life …

9.5 What Are Fossils? ● Fossils → any remains, traces, or imprints of a plant or animal that are preserved in a rock or sediment ● Trace fossils → rocks contain other features made by animals that moved across the surface or burrowed into soft sediment ● Most important factors of fossil preservation: ○ Hard parts ○ Rapid burial

9.6 How and Why Did Living Things Change Through Geologic Time? ● Faunal succession → fossils change upward from older layers of sedimentary rock to younger layers ○ Helped geologists identify time periods defined by major changes in life on Earth Cenozoic

Mesozoic

Paleozoic

Precambrian

66 Ma - present

252 Ma - 66 Ma

541 Ma - 252 Ma

Age of mammals / became a dominant type of life on Earth

Age of dinosaurs / rose to dominance & ends w/ extinction

Marine animals / some ~90% of geologic time; land animals / ends with mostly only simple life the Great Dying forms existed

5400 Ma - 541 Ma

9.8 How Was the Geologic Timescale Developed? ● Geologic time scale was devised by using fossils or by noting the absence of fossils ● Largest time intervals shown below are eras ○ Boundaries between eras are marked by major in the fossils, specifically

(extinction) of many species and families of creatures -- mass extinctions

9.9 What Is the Evidence for the Age of the Earth? ● Earth is 4.55 billion years old ● Oldest rocks = metamorphic ● Evidence that Earth’s History is Not Short: ○ Seasonal layers in tree rings ○ Seasonal layers in ice cores ○ Seasonal layers in lake sediment ○ Measured rates of modern plate movement are consistent with long-term rates ● What is the evidence for the age of the Earth? ○ Age of meteorites ○ Dated moon rocks ○ Oldest dates on Earth rocks ○ Data from astronomy on the age of the Solar System and Universe

9.10 What Events Occurred Early In Earth’s History and How Did Earth Change Over Time? ● Earth’s earliest chapters were dominated by impact cratering ● Lack of oxygen in Earth’s early history has many implications ○ Increase in oxygen caused iron to be deposited in ocean

9.11 What Were Some Milestones In the Early History of Life on Earth? ● Some of Earth’s first inhabitants were early forms of algae, represented by fossils called stromatolites found in Austrailan rocks that are 3.5 billion years old ● Precambrian Life ○ Stromatolites (3.5 GPA) ● Cambrian Explosion ○ 541 Ma ○ Shelled organisms ● Paleozoic Life ○ Corals, fish, crinoids, amphibians & reptiles

○ Organism migrate onto lead ○ Early, middle and late paleozoic

9.12 What Were Some Milestones In the Later History of Life on Earth? ● Mesozoic ○ Dinosaurs ○ Early mesozoic: triassic ○ Middle mesozoic: jurassic ○ Late mesozoic: cretaceous ● → KT Extinction ● Cenozoic ○ Age of the mammals ○ Homo sapiens appear 300,000 years ago https://quizlet.com/57172852/geology-chapter-9-geologic-time-flash-cards/ https://quizlet.com/98624499/geology-chapter-9-geologic-time-and-earthquakes-flash-cards/

Seafloor and Continental Margins - Chapter 10 10.1 How do we explore the seafloor? ● Drilling process ○ Yields cylinder-shaped samples, called drill core, which provide many types of data ● Seismic-reflection technique is widely used in exploring for oil and natural gas beneath the seas and on land

10.2 What processes occur at mid-ocean ridges? ● New crust forms ● Tectonic plates diverge ● *Why are the ridges taller than the surrounding seafloor? ● Hydrothermal vents

10.3 What are the major features of the deep ocean?

● Beneath the world’s oceans lie rugged mountains, active rifts, gentle plains, broad plateaus, and deep trenches ○ Abyssal plains, seamounts, trenches, island arc systems ● Oldest oceanic crust in any ocean is the most distant from mid-ocean ridges

10.4 How do oceanic islands, seamounts, and oceanic plateaus form? ● Oceanic Islands & Seamounts ○ Most are made of mafic to intermediate volcanic rocks and are formed by a series of volcanic eruptions on the seafloor ○ Magmatism, underlying hot spot → continued eruptions → top of mountain is beveled off by wave erosion ● Oceanic Plateaus ○ Some large regions of the seafloor rise a kilometer or more above their surroundings, forming oceanic plateaus

10.5 What Processes Form Island Arcs? ● Island arcs form when… ○ One oceanic plate subducts beneath another ○ Subduction creates a trench and generates magma that forms an arcuate belt of volcanic islands

10.6/10.7 Smaller Seas ● Extension of the back-arc basin due to trench rollback ○ Philippine Sea

● Extension and depression of continental crust ○ North sea ● Divergent plate boundary ○ Red sea

10.9 What is the Geology of the Continental Margins? ● Continental shelf ● Continental slope ● Rise ● Submarine canyons ● Passive margins ● Turbidity currents

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Mountains, Basins and Continents - Chapter 11 11.1-11.3 Why are there mountains? ● Density and thickness of crust control regional elevation ● Causes elevation to decrease: normal faulting→ decreases crustal thickness ○ Erosion ○ Rocks contract when they cool ● Causes elevation to increase: Crust is compressed ○ Magma beneath the crust heats it ○ When material is added to the surface ● Oceanic crust is denser than continental ● Where do mountain belts form?

○ Subduction Zones ○ Continental Collisions ○ Mantle Upwelling ■ Hot spots ■ Rifting ● Isostasy: regional elevations adjust to types and thicknesses of rocks at depth ● Isostatic Rebound: material erodes from a mountain belt & buoyant crust is uplift- results in continental shelf ● Regional Mountains: super long, involve peaks & uplifted or thickened crust ● Local mountains: smaller, rest upon/ supported by the crust ○ Form: by volcanic eruption, faults, folding, erosion

11.4-11.6 Why are there basins? ● Form on both oceanic and continental plates and along plate margins ● Passive Margin: largest type of basin ○ Continental margin that is not a plate boundary ○ Includes continental shelf, rise, and slope underlain by thin, rifted crust ○ Shallow- water for diverse life with sediment from continent ● Reverse and thrust faults: occurs when crust is depressed by the weight of trust sheets ● Strike- Slip Faults: basins develop along these faults ● At subduction zones beneath continents, various processes create mountains and basins. ○ Ocean- Continent Convergence: where the oceanic plate subducts beneath a continental plate ● Continental Collisions: the convergence of two tectonic plates that each carry continental crust- one continent is generally too buoyant to be subducted deeply→ the whole region lifted up ● How is the age of basin determined? ○ Describe and measure layers ○ Isotopic dating of volcanic rocks and fossils ○ Age, thickness, and character of sediments record when and how fast a basin formed

● Hot Spot: within a continental plate is marked by high elevations, abundant volcanism, and continental rifting ○ Have helped define the outlines of the continents by shaping the boundary along which continents separate from one another

11.8 What features characterize the interiors of the continents? How does the creation of continents differ from the creation of the ocean basins? ● Characteristics: Central region of older crystalline rocks surrounded by a thin veneer of younger, nearly flat-lying sedimentary layers ○ Continental shield ○ Continental platform ○ Coastal plain

11.9 What are tectonic terrains? ● A bounded by faults and having rocks, structures, fossils, and other geologic aspects that are unlike those in adjacent regions ● Tectonic terrain is different than the adjacent rocks ○ Different sequence of rocks ○ Different ages ● Typically terrains are added by subduction

11.10 How do continents form? ● Tectonics constantly reshape continents ○ Pieces can be removed by rifting or added by accretion of tectonic terraces ○ Are internally rearranged as areas are shortened during compression, stretched during extension, and shifted horizontally by strike-slip faults https://quizlet.com/282986639/mountains-basins-and-continents-ch11-flash-cards/ https://quizlet.com/333844092/chapter-11-mountains-basins-and-continents-flash-cards/

Earthquakes - Chapter 12 12.1 What Is An Earthquake?

● Earthquake → an event during which energy stored in rocks is released ○ Result is the movement of the crust ● Earthquakes are caused by faulting, volcanoes, or landslides ● Hypocenter/focus = place where the earthquake is generated ● Epicenter = point on Earth’s surface directly above where the earthquake occurs

12.2 What Causes Earthquakes? ● Earthquakes occur because of movement along faults ○ Pre-slip & elastic strain ○ Slip & earthquake ○ Post-slip

12.3 Where Do Most Earthquakes Occur? ● Most earthquakes occur along plate boundaries ○ 90% of significant earthquakes occur along subduction zones

12.4 What Causes Earthquakes Along Plate Boundaries and Within Plates? ● Divergent boundaries ○ Shallow ● Convergent boundaries ○ Large, deep

12.5 How Do Earthquake Waves Travel? How Are Seismic Waves Measured? ● Body Waves ○ Primary (P) Waves ■ Fastest ■ Compression ■ Travel through liquid & solids ○ Secondary (S) Waves ■ Slower than P-Waves ■ Travel only through solids

● Surface Waves ○ Travel along the Earth’s surface ○ Cause the most damage

12.6 How Do We Determine the Location and Size of An Earthquake? ● How do we locate earthquakes? ○ Seismometer network senses a quake ○ Select earthquake records ○ Estimate station distance from epicenter ○ Triangulate the epicenter ● How do we measure earthquake size? ○ Richter Scale ■ Amplitude of the largest S-wave

12.14 How Do We Explore the Earth’s Subsurface? ● Direct observations ○ Igneous inclusions ○ Mining ○ Drill holes (< 3 miles) ● Indirect observations ○ Seismic surveys ○ Geophysical surveys ■ Gravity ■ Magnetic field ■ Resistivity (electrical)

12.15 What Do Seismic Waves Indicate About the Earth’s Interior? ● Changes in density, caused by temperature, pressure and compositional variations, cause seismic waves to change velocity and direction

12.16 How Do We Investigate Deep Processes? ● Rocks formed at depth

● Laboratory ● Numerical models

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