earth science exam 2

Strike (42)

Book: The compass orientation of a horizontal line on a plane.

Powerpoint: The orientation of a line formed by the intersection of a horizontal plane and the dipping surface

Dip (42)

Book: The angle of a plane's slope as measured in a vertical plane perpendicular to the strike.

Powerpoint: The line along the steepest dip of the plane.

Dip Angle (Powerpoint): The angle between the horizon and the dipping plane

Stress (10-19)

Book: The push, pull, or shear that a material feels when subjected to a force; formally, the force applied per unit area over which the force acts

Powerpoint: The force applied to cause deformation and strain

Stress leads to deformation results in strain

Compression, squeezing, tension, pulling

Shear: sliding

Deformation (5-8, 10, 23)

Powerpoint: The act of displacing, rotating, or distotring a rock

Deformed Rocks: Rocks that have been tilted, folded, faulted, or squeezed to change grain shapes or develop a fabric

Undeformed Rocks

Rocks that have not been disturbed since lithification

Modes of deformation

Displacement, rotation, distortion

Qualities of deformation

brittle, ductile/plastic

Factors that influence types of deformation

temperature and pressure

Displacement (6)

Deformation mode

Change in location

When a block moves from one place to another, typically accommodated by slip along a fault

Rotation (7)

Deformation mode

Change in orientation

When a body of rock undergoes tilting, can be accompanied by faulting or folding

Distortion (8)

Form of deformation

Change in shape

Can be due to large-scale changes like folding or microscopic changes in grain shapes

Strain (10-13, 15-19)

Book: The change in shape of an object in response to deformation (i.e. as a result of the application of a stress)

Powerpoint: The change observed in the rock. Results from deformation

Shear: tilting and change in angular relationships within the object

types of strain

Contraction, shortening, elongation, stretching (can take place in any direction)

Elastic Behavior

A response of a material to stress, during which the material changes shape; the amount of change depends on the magnitude of stress, and the change disappears when stress is removed; the behavior occurs when chemical bonds bend or stretch, but do not break.

Plastic/Ductile Deformation (21-23)

Book: The deformational process in which mineral grains behave like plastic and, when compressed or sheared, become flattened or elongate without cracking or breaking

Powerpoint: Deformation without cracking and breaking. Material flows. Bonds between atoms break and quickly reform.

Higher temperature and pressure lead to plastic/ductile deformation

Brittle Deformation (20-23)

Book: The cracking and fracturing of a material subjected to stress

Powerpoint: Deformation through cracking and breaking. Bonds between atoms break and stay broken. Lower temperature and lower pressure leads to brittle deformation

Joints, veins, and faults

Joints (24, 25, 159-163)

Textbook: Naturally formed cracks in rocks

Powerpoint: Natural cracks within a rock body.

Form in response to tensional stress (cooling in igneous rocks, pressure decrease as rock body is unroofed/unburied)

Faults (5-7, 27-36)

Textbook: A fracture on which one body of rock slides past another

Dip slip (27-29, 42)

Dip can be vertical, horizontal, or anywhere in between

Shear sense across fault (relative direction of each body of rock on either side of fault)

Strike-Slip (30)

Textbook: A fault in which one block slides horizontally past another (and therefore parallel to the strike line), so there is no relative vertical motion.

Normal Fault (28, 63)

Textbook: A fault in which the hanging-wall block move down the slope of the fault\

Powerpoint: stretching of the crust

Tensional stress leads to normal faulting

Hanging wall moves down

Reverse Fault (28)

Hanging wall moves up. Shortening of crust >30 degree dip/slope of fault surface (steep)

Thrust Fault (28)

Textbook: A steeply dipping fault on which the hanging-wall block slides up

Powerpoint: Hanging wall moves up. <30 degree dip/slope of fault surface (shallow)

Shortening of crust

Transform Faults

A fault marking a transform plate boundary; along mid-ocean ridges, transform faults are the actively slipping segment of a fracture zone between two ridge segments

A boundary at which one lithosphere plate slips laterally past another

Hanging Wall (27, 28)

Block above fault surface

Moves up in reverse/thrust faults, down in normal faults

Footwall (27)

Block below fault surface

Compression or extension.....vs. fault type (28)

Reverse and Thrust = compression

Normal = extension

Right-Lateral (30)

Block across fault moves right

Left-Lateral (30)

Block across fault moves left

Anticline (39)

Textbook: A fold with an arch-like shape in which the limbs dip away from the hinge

Powerpoint: Fold that resembles an arch. Limbs point away from hinge. Oldest layers exposed in the middle of the fold on Earth's surface

non-plunging and plunging

Nonplunging anticline (39)

Hinge line is horizontal. Map pattern is straight lines

Plunging anticline (39)

Hinge line is tilted. Map pattern is curves

Syncline (40)

Textbook: A trough-shaped fold whose limbs dip toward the hinge

Powerpoint: A fold that resembles a trough. Limbs point towards the hinge. Youngest layers exposed in the middle of the fold on Earth's surface

Monocline (40)

A bend or a step of rock layers that are otherwise horizontal

Fold (38-41)

Textbook: A bend or wrinkle of rock layers or foliation; folds form as a consequence of ductile deformation

Powerpoint: A curve in the shape of a rock layer. Main types are anticline, syncline, monocline, domes, and basins.

Axis?

?

Limb (38)

Textbook: The side of a fold, showing less curvature than at the hinge

Powerpoint: Straighter sides (arms) of a fold

Hinge (38)

Textbook: Portion of a fold where curvature is greatest

Powerpoint: The line at the center of the fold where the curvature is the greatest

Axial Plane

Imaginary plane that contains the hinge lines of successive layers and effectively divides the fold into two halves.

Domes (41)

Textbook: Folded or arched layers with the shape of an overturned bowl

Powerpoint: A fold that resembles an upside-down bowl

Basins (41)

Textbook: A fold or depression shaped like a right-side-up bowl

Powerpoint: A fold that resembles an upright bowl

Position vs. Age of rocks in anticlines & synclines (39, 40)

Anticline: Oldest layers exposed in the middle of the fold on Earth's surface

Syncline: Youngest layers exposed in the middle of the fold on Earth's surface

Mountains

Mountain Belt: An elongate band of mountains, formed as the result of an orogeny.

Mountain Building: The process of generating a mountain range.

Mountain (Alpine) Glacier :A glacier that exists in or adjacent to a mountainous region.

Continental Shield (290)

An older, interior region of a continent

Active Margins

A continental margin that is also a plate boundary

Passive Margins

A continental margin that does not coincide with a plate boundary, and therefore does not display seismicity (passive continental margin)

Orogenesis

The processes that collectively result in the formation of mountains.

Orogeny

A mountain-building event

Terrane

A piece of lithosphere that has a unique geologic history and that may be part of a larger piece of lithosphere, such as a continent

Angle of Repose

The angle of the steepest slope that a pile of uncemented material can attain without collapsing from the pull of gravity

Controls on Ang. of Repose

The angle depends partly on the shape and size of grains, which determine the amount of friction across grain boundaries. For example, steeper angles of repose tend to form on slopes composed of irregularly shaped grains

Weathering (158, 178-184)

Textbook: The processes that break up and corrode solid rock, eventually transforming it into sediment

Powerpoint: Physical and or/chemical processes that corrode and break up solid rock

Types: Physical, chemical

Influenced by lithology

Erosion (158)

Textbook: The grinding away and removal of the Earth's surface materials by moving water, air, or ice

Powerpoint: The breaking off and removal of rock or sediment

Physical/Mechanical Weathering (159, 179, 187)

Textbook: The process in which intact rock breaks into smaller grains or chunks

Powerpoint: The mechanical breakdown of rock

Types: jointing, frost wedging, salt wedging, root wedging, thermal expansion, animal attack

Increases surface area

Produces loose debris, ions in solution, and new weathering products

Jointing (160-163)

Joint: a natural crack in a rock

Type of physical weathering

Influenced by lithology

Sedimentary layers typically break into rectangular blocks

Breaking off and falling of the blocks results in a talus apron

Frost Wedging (164-166)

Type of physical weathering

Definition: Water expands as it freezes and pushes pieces of rock apart

Water expands about 9-10% in volume when it freezes

More effective in mechanically weak rocks

Salt Wedging (167)

Precipitation of salt in pores between grains pushes pieces of rock apart

Salt can be dissolved and traveling in groundwater then precipitate in bedrock

Along coastlines, salt spray from the ocean can precipitate into rock faces

Most common in arid regions

Form of physical weathering

Root Wedging (168)

As roots grow, they push joints open

Form of physical weathering

Thermal expansion (169)

Heating of the surface of the rock by the sun

Leads to differential expansion

Can occur between surface and interior of rock as well as between different minerals within the rock

Results in "peeling" of the outer layers in a process known as exfoliation

Form of physical weathering

Animal Attack (170)

Burrowing creatures that remove rock fragments

Smaller footprint, but the rates of weathering are much faster

Form of physical weathering

Chemical Weathering (159, 178-181)

Textbook: The process in which chemical reactions alter or destroy minerals when rock comes in contact with water solutions and/or air

Powerpoint: Chemical reactions that alter or destroy minerals

Forms: dissolution, hydrolysis, oxidation, hydration

Works on a surface, removes edges/corner

chemical weathering process

Removes cements and weaker minerals -> loss of material permits rocks to break apart mechanically -> breaking apart results in more surface area -> increased surface area = increased chemical weathering

Dissolution (172-174)

Transformation of a compound into free ions with the introduction of a solvent (water)

Affects primarily salts and carbonates

Silicate minerals can dissolve slightly

Constituents released from parent rock into surface or groundwater and typically removed from weathering site = voids

Form of chemical weathering

Hydrolysis (175)

Water reacts chemically with minerals and breaks them down to form other minerals

Water molecule dissociates into H+ and (OH)- ions causing water to become more acidic

Produces secondary minerals - dominantly clay minerals and Fe/Al oxides/hydroxides formed in situ by chemical recombination and crystallization

Form of chemical weathering

Oxidation (176)

Reactions transform iron-bearing minerals to Fe-oxide and Fe-hydroxide minerals

Combination of oxygen with a mineral to form one or more minerals that are more "oxidized"

Causes rocks to "rust"

Hydration (177)

Absorption of water into crystal structure of minerals causing swelling

Anhydrite + H2O = gypsum

Form of chemical weathering

Graded Bed (289)

Vertical change in particle sizes

Sedimentary structures

Alluvial Fan

A gently sloping apron of sediment dropped by an ephemeral stream at the base of a mountain in arid or semiarid regions

Relative Age/Dating (97)

The age of one feature with respect to another.

Numerical Dating (97)

Aka absolute age, an age given in years. Radiometric/radioisotopic dating

Geologic principles (104)

7 geological principles

• Uniformitarianism

• Original horizontality

• Superposition

• Lateral continuity

• Cross-cutting relations

• Baked contacts

• Inclusions

Principle of Uniformitarianism (69-71)

Physical processes we observe today also operated in Earth's past at the same rates. No need for catastrophic events - instead, the Earth is the result of slow processes over vast amounts of time

The present is the key to the past

Principle of Original Horizontality (72, 73)

Sediment is deposited in horizontal layers, so tilting, faulting, or folding in sedimentary rocks occurred after deposition

Principle of Superposition (74, 75)

In a sequence of sedimentary rock layers, each layer is younger than the layers below it

Principle of Lateral Continuity (76, 77)

Sediments generally accumulate in laterally continuous sheets across a region - erosion causes beds to become discontinuous

Principle of Cross-Cutting Relationship (78, 79)

If one geologic feature cross-cuts another, the feature that has been cut is older

Principle of Baked Contacts (80)

An igneous intrusion "bakes" the rocks it intrudes, so the rock that has been baked must be older than the intrusion

Principle of Inclusions (81, 82)

A rock containing a piece of another rock must be younger than the included fragment

Principle of Fossil Succession (99, 100)

Different fossil species always appear and disappear int he same order at distinct locations

Once a fossil species goes extinct, it disappears and cannot reappear in younger rocks

Fossil Range (100)

Interval over which a fossil occurs

Fossil Assemblage (100)

A group of fossils found together in a layer of rock

Index Fossils (100)

Textbook: A fossil of an organism that lived during a relatively short period of time over a relatively large area of the Earth, and can be used for stratigraphic correlation

Powerpoint: Fossil species that are geographically widespread but occur over a short interval of geologic time

Biotic Succession

the development of biological communities in the same area in an era.

Biostratigraphy

the branch of stratigraphy concerned with fossils and their use in dating rock formations

Stratigraphic range

arrangement and succession of strata, or layers, as well as the origin, composition and distribution of these geological strata

Stratigraphic Correlation (101-103)

Across very broad regions, the depositional setting or sediment source can change

Therefore, stratigraphic successions can vary over space and lithology can't be used alone to correlate

Combining fossils and lithology allows for more complete correlations over broad regions

Nonconformity (93)

Textbook: A type of unconformity at which sedimentary rocks overlie basement (older intrusive igneous rocks and/or metamorphic rocks)

Powerpoint: Strata are deposited, granite intrudes, erosion down to granite, new sediment

Unconformity

A boundary between two different rock sequences representing an interval of time during which strata were not deposited and/or were eroded

Angular Unconformity (68, 92)

Textbook: An unconformity in which the strata below were tilted or folded before the unconformity developed; strata below the unconformity therefore have a different tilt than strata above

Powerpoint: Strata below are tilted, eroded, then new strata are deposited on top

Disconformity (94)

Textbook: An unconformity parallel to the two sedimentary sequences it separates

Powerpoint: Strata are deposited, deposition stops and erosion removes some, deposition continues

Geologic Time Scale (Eon, etc.)

154

The last 539 million years constitute the Phanerozoic Eon, and all time before that makes up the Precambrian. The Precambrian can be further divided into three main intervals named, from oldest to youngest: the Hadean, the Archean, and the Proterozoic Eons. The Phanerozoic Eon, in turn, can be divided into three main intervals named, from oldest to youngest: the Paleozoic, the Mesozoic, and the Cenozoic Eras.

Radioactive Decay (106)

Textbook: The process by which a radioactive atom undergoes fission or releases particles, thereby being transformed into a new element

Powerpoint: Spontaneous release of energy stored in nuclear bonds, which causes the parent atom to form (or transform into) a new daughter atom

Parent Isotope (106, 107)

A radioactive isotope that undergoes decay

Daughter Isotope (106, 107)

The decay product of radioactive decay

Radioactive Half-Life (107)

Textbook: The time it takes for half of a group of a radioactive element's isotopes to decay

Powerpoint: How long it takes for half a group of parent atoms to decay to daughter atoms

Climate change (208, 230, 234-237, 242-257, 263-288)

Transformations or modifications in the Earth's climate over time

Greenhouse effect

The trapping of heat in the Earth's atmosphere by carbon dioxide and other greenhouse gases, which absorb infrared radiation; somewhat analogous to the effect of glass in a greenhouse

Oxygen Isotopes (239, 288)

Record past changes in glacial ice volume.

Using oxygen isotopes, we can get a record of past changes in global temperature

Climate (251)

Textbook: The average weather conditions, along with the range of conditions, of a region over a year

Powerpoint: The characteristic weather of a region averaged over some significant interval of time, particularly as regards temperature and precipitation

Weather (251)

Textbook: Local-scale conditions as defined by temperature, air pressure, relative humidity, and wind speed

Powerpoint: State of Earth's atmosphere at a specific place and time, particularly as regards to temperature, barometric pressure, wind velocity, humidity, clouds, and precipitation