Geology Final exam

index fossils-useful with correlation

"Time-Indicators" • Geographically widespread • But appeared and disappeared quickly. • Lived a short span of geologic time • Examples: Trilobites and Forams (Foraminifera) Fossil assemblages ( groups of fossils) are also "time-indicators

Coastal Zone is a Dynamic Interface

Beach is the gently sloping fringe of sediment along the shore that is influenced by waves, tides, and currents. Other coastal environments include the nearshore, dunes, estuaries, lagoons, and marshes.

groundwater

Groundwater represents the largest reservoir of freshwater that is readily available to humans. ✓Fills pore spaces between grains of soil and sediment, and narrow joints and fractures in bedrock. Groundwater is the liquid water that resides within sediment or rock under the surface of the Earth • Dissolution of limestone creates caverns and sinkholes • Important source of freshwater

erosion control

Hard structures • Used for stabilizing coastlines, reducing wave heights, and trapping sediment • Shore-parallel • Breakwaters reduce wave energy • Seawalls and riprap reduces wave attack and "holds" the land in place • Used for stabilizing coastlines, reducing wave heights, and trapping sediment • Shore-perpendicular • Groins trap sediment moving alongshore (longshore drift) • Jetties stop sediment from filling in navigational waterways (inlets)

limestone

Limestone is a rock composed of the mineral: • Calcite (CaCO3) • Readily dissolves in the presence of slightly acidic groundwater. In areas of humid climate • Wet season or significant rain Rain water seeps downward through the soil • Becomes slightly acidic groundwater from reacting with organic matter and minerals into openings in the limestone bedrock • Gradually dissolving the rock matrix.

longitudinal profile of a stream

The general longitudinal profile is concave-up curve, decreasing in steepness and flow velocity as you move down stream from source to mouth

wind generates waves

Wind blowing over water generates waves • Wave height (distance from crest to trough) • Wavelength (distance between wave crests) • Wave period (time between successive wave crests)

a benchmark is

a permanent marker on the ground that indicates location and elevation

numerical dating

based on radioactive decay of atoms in minerals isotopes stable radioactive

age of coal swamps

carboniferous period

age of mammals

cenozoic era

cross sectional profile of a stream

changes with position along the stream from headwaters to mouth Narrow valleys changing to broader channels

small tick marks on contour lines indicate

depressions

wavelength

distance between wave crests

wave height

distance from crest to trough

sea arches collapse into sea stacks

due to erosion

estuaries

embayment where marine water meets fresh water

mouth

end of stream

The principle of superstition can be used to determine the relative ages of all of these except

folded sedimentary rocks

meandering streams

gentle gradient • Meandering streams form where stream's gradient is very gentle, and the flow cannot maintain a straight line Meandering streams change shape over time. • Erosion occurs faster on the outer curve (cut banks), and • Deposition on the inner curve (point bars). • Eventually, cutoff isolates oxbow lakes.

fjords

glacially carved valleys filled with seawater

local base level

location of base level upstream of the mouth

barrier islands

low ridges of sand that parallel the coast Found along the Atlantic and Gulf Coastal Plain, they are narrow and long ephemeral islands that are subject to overwash during storms Can originate as: - Spits- Sand piled up offshore- Flooded dunes from the last glacial period

movement in the saturated zone

more complex flow due to variability in pressure; following a more curved path

contour lines on a map connect points

of equal elevation

age of fishes

ordovician period

movement in the unsaturated zone

percolation straight down via gravity

sea level rise

rising seas can inundate low-lying areas, infiltrate groundwater, and exacerbate erosion

the zero contour line is also known as

sea level

head

source of stream

stream rejuvenation

stream downcutting towards base level

The term relative age refers to

whether a feature is older or younger than another feature

depositional features

• Point bars (mounds of sediment on inside of river bend, or meander) • Floodplains develop during flooding (exceeding channel)

flow velocity

- Channel slope • Higher slope, higher flow - Channel cross-sectional shape • Ratio influences velocity - Channel size and roughness • Slower near bed and edges - Discharge (D) • Volume of water flowing past a certain point in a given unit of time (typically cubic meters per second)

permanent streams

- Contain flowing water all year, typically in temperate climates where channel intersects the water table

drainage patterns

- Dendritic: flow over uniform surface material - Radial: conical flow away from topographic high point - Rectangular: flow in pre-existing fractures and joints - Trellis: flow down parallel valleys and ridges joining a trunk stream - Parallel: parallel flows on steep, uniform slopes

emergent coasts

- Develop because of Uplift or a drop in sea level• Examples: - California coast - Subduction - Hudson Bay -Isostatic rebound - Features of an emergent coast• Wave-cut cliffs• Wave-cut platforms• Marine terraces • Little space (due to narrow continental shelf) for sediment to accumulate; rocky features often under "wave attack" causing erosion

caves and caverns

- Dissolution of limestone by acidic groundwater at or just below the water table - Form speleothems• Stalactites• Stalagmites

transport in streams

- Dissolved load: ions of soluble minerals - Suspended load: small solid grains within the water column - Bedload: larger grains bouncing (saltation), rolling, and sliding along the stream bed - Depends on discharge • Competence -maximum size is transported • Capacity -maximum load (volume) is transported

• Laminar versus turbulent flow

- Flow is not the same along or across a river - Laminar flow: straight and parallel contours of flow - Turbulent flow: twisting, swirling eddies of the flow ✓These processes within streams are important in erosion, transport, and deposition of sediment across continents

mining groundwater

- Imbalances, or lowered water tables, arise from overuse/withdraw (a, b), drought (c), or water diversion from recharge area (d, e) • Reversing the flow direction of groundwater • Contaminant flow in groundwater - Cone of depression Saltwater intrusion

geysers

- Intermittent hot springs or fountains where water is ejected with great force at various intervals

wells

- Ordinary well: base of well penetrates aquifer below the water table - Issues with drawdown, cone of depression if pumped too fast (without recharge) - Artesian system: pressure causes water to rise above level of a confined aquifer to reach the surface - Reason water flows from your faucet! • Potentiometric surface is imaginary plane where water rises

ephemeral streams

- Periodically contain flowing water, where channel lies above the water table in areas with rainy and dry seasons

erosion in streams

- Scour (carrying away loose fragments of sediment - Breaking and lifting - Abrasion (like sandpaper when flow has sediments) creating bowl -shaped depressions (or potholes) - Dissolution

groundwater contamination

- Septic tanks, broken or leaking sewer lines, farm wastes, leachate from landfills, fertilizers, pesticides, leaking underground storage tanks e.g. gasoline tanks at gas stations.

sedimentary structures

- Strata (beds) -layering, the most common and characteristic feature of sedimentary rocks. - Bedding planes - separate strata, mark the end of one episode of sedimentation and the beginning of another.

saturated vs unsaturated zone

- Unsaturated: water and air within pores - Saturated: water completely fills pores = groundwater

deposition in streams

- Velocity decrease →competence decrease • Sediment drops out = alluvium (or fluvial deposits) • Water sorts by size

conditions for sinkholes

1. Lowering of the Water Table Drought - Lack of rainfall Pumping of groundwater wells: Agriculture, Water Supply 2. Rapid Raising of the Water Table temporarily raises the water table Following Tropical Storms - heavy rainfall 3. Changing where the Water Drains Development - Buildings, parking lotsDredgingBuilding ReservoirsCanals to Channel Surface Water

variable coastal features

1. Proximity sediment source, currents 2. Tectonics -proximity to plate boundary (active vs. passive) 3. Geologic controls (topography, slope) 4. Wind, weather, nearshore processes 5. Coastal configuration (open or protected) 6. Sea level (emergent vs. submergent coasts)

what is a beach

A Beach is an accumulation of sediment found along the landward margin of an ocean (or lake) The sediment source reflects locally abundant material, and those sediments brought in by currents. The sand grains are rounded by abrasion and reflects how far the grains have traveled and/or how long they have been on the beach.

stalactite

A calcite deposit that hangs from the roof of a cave

stalagmite

A cone-shaped calcite deposit that builds up from the floor of a cave

coastal erosion

Loss of sediment from beaches, dunes, and wetlands; storms, interruption of sediment transported to or along the coast, and construction are common causes of erosion

ocean water is salty

Ocean water contains dissolved ions eroded from rocks • chloride (Cl−)• sodium (Na+)• sulfate (SO24−)• magnesium (Mg2+)• calcium (Ca2+)• potassium (K+) When precipitated, this will form minerals and salt (e.g. NaCl)

coastal hazards

Oil spills, influx of nutrients producing dead zones and harmful algal blooms, reef bleaching and destruction, and garbage dumping are just a few examples of how water quality can be degraded by human activities.

Nicolaus Steno -1669

Steno looked at sedimentary structures and conceptualized that rock strata could be put into a chronological time series. He developed the following principles that enabled relative dating of rock. • Principle of Superposition • Principle of Original Horizontality • Principle of Lateral Continuity • Principle of Cross-cutting relationships • Principal of Inclusions

hydraulic conductivity

Velocity of groundwater flow varies with permeability of the material: hydraulic conductivity

The principle of inclusion states that

a sedimentary rock must be younger than the clasts that it contains

radioactive decay

age determined by ratio of parent to daughter isotopes half life-Always 50 % of atoms(the number of atoms decreases with each half-life)

thermohaline circulation

an oceanic circulation pattern that drives the mixing of surface water and deep water

contour lines on a topographic map

are spaced at equal distances from one another horizontally

drainage basin

area of land drained by river system

Waves bend (or refract) when coming into shore

at a large angle, resulting in waves that are mostly shore-normal (<5 degrees). • Produces longshore currents • Important in sediment transport along the shore (land-water interface)

age of trilobites

cambrian period

If a sequence of sedimentary rocks has been folded and is now vertical,

graded bedding can help determine whether some beds are older or younger than the beds next to them

stream piracy

headward erosion of one stream intersects another

divide

imaginary boundary of drainage basins- Separate flow into different oceans example; continental divide

runoff

is all water flowing on the surface of the Earth, including -Sheetwash: thin film of water flowing downslope, and -Streams: any water that flows in a channel, regardless of size • A channel: elongate depression or trough • A river carries a substantial amount of water and has many tributaries - Headwaters: source of stream (upstream) - Trunk stream: array of linked streams - Mouth: end of stream (downstream)

hydraulic head

is the energy available to drive flow • Velocity of groundwater flow is proportional to the slope of the water table: hydraulic gradient

water table

is the horizon that separates the unsaturated and saturated zones • Shape of the water table mimics the overlying land surface (a subdued replica below ground)

closure temperature

is the time during the formation of the mineral (when cooling) when isotopes are no longer free to move. igneous rocks

age of reptiles

mesozoic era

springs

natural outlets where groundwater flows or seeps onto the Earth's surface - Used for drinking or irrigation (or swimming!)

The magnitude of geologic time is often referred to as deep time.

numerical- actual age relative- whether a feature is older or younger than another feature

sinkholes

removal of bedrock causing instability of soil and rock from above, resulting in collapse Sinkholes are naturally occurring, roughly circular depression or holes in the land surface. They can be shallow or deep, small or large, but all are a result of the dissolving of the underlying limestone.

ultimate base level

sea level; the lowest possible elevation of a river/stream

An angular unconformity is evidence that

there is an incomplete geologic record preserved in an area

wave period

time between successive wave crests

longshore current

wave-induced along the beach (e.g., north and south along south FL beaches)

cross shore currents

wave-induced undertow and rip currents directed on and offshore

interface

where the sky meets the land and sea... • Different systems interacting • Oceans: interact with all of Earth's spheres • Coasts: interface with land, sea, and atmosphere

disconformity

• "Disruption" in sediment accumulation • Layers deposit →layers eroded →new layers deposited • Sedimentary rocks

nonconformity

• "Not" the same rock: sediment deposited (i.e., sedimentary rock) after older rocks (i.e., metamorphic or igneous rocks) were eroded • Erosion of existing rock →new layers deposited

conditions for fossil preservation

• (Low) oxygen content in depositional environment • Rapid burial • Presence of hard parts

principle of inclusions

• A rock containing a fragment of another rock (or inclusion) is younger than the inclusion • Applies to all rock types

freshwater withdrawals

• Agricultural irrigation (≈ 70%) • Urban water use (≈30%)

alluvial fans and braided streams

• Alluvial fans form where the river mouth opens at the base of a mountain, depositing a wedge (or fan) shaped apron of sediment (top right) • Braided streams form where large quantities of sediment are carried during periodic high flow, then "choke" the river with deposits during lower flows (bottom right)

aquifers and aquatards

• Aquifers- Permeable rock strata or sediment that transmits groundwater freely • Aquatards- Impermeable layers hindering or preventing water movement

base level of streams

• Base level = lowest elevation of a stream's channel surface - Limits stream erosion - Stream surface cannot be lower than base level - Base level changes relate to changes in deposition or erosion

unconformities

• Changes in depositional environments are "recorded" in the rocks. • Erosion (unconformities) "erase" that record • Boundary surface between units that represents a period of non-deposition or erosion • "Gap" in the geologic record because material removed

organic coasts

• Coastal environments where living organisms control the landform • Wetland: vegetated coastal environment (includes marsh, mangrove, bogs) • Coral reefs: organisms secreting calcite

deltas

• Deltas are wedge-shaped deposits of sediment where a river enters a water body (base level) • Sediment is reworked depending on dominant process within the body of water at the river mouth A) "delta" shaped delta where wave energy dominates B) "arc" shaped delta where tidal currents dominate C) "birds foot" shaped delta where river flow dominates

tides

• Due to gravitational attraction of the Sun and Moon and centrifugal force produced by Earth-Moon system revolving around its center of mass • Range: difference between high and low tide • Varies with alignment of sun, moon, and Earth • Neap: smaller tidal range when moon is orthogonal (at 90° angle) to the sun and Earth • Spring: higher tidal range when moon, sun, and Earth are all aligned

flooding hazards

• Flooding can present hazards for river-adjacent communities - Slow-onset floods happen due to rapid snow melt or rains, sustained rains for long periods of time, or when a storm remains stationary and drops high quantities of rainwater - Flash floods occur when floodwaters rise rapidly

principle of faunal (fossil) succession

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

3 zones of streams

• Headwaters: erosion (sediment production) • Trunk stream: transportation • Mouth: deposition

hot springs

• Hydrothermal feature- Groundwater circulating at depth becomes heated due to the geothermal gradient or nearby magma plume

principle of baked contacts

• Igneous intrusions "bake" (or metamorphose) surrounding rocks; thus the rock that has been "baked" is older than the intrusion.

principle of cross cutting

• Igneous intrusions, geologic structures • If feature cuts across another, the feature that was "cut" is older 1. Sediments deposited in layers and form into strata of sedimentary rock. 2. Igneous dike cuts across existing layers. 3. Movement along the fault offsets the rock strata and the dike.

currents

• Important in global circulation patterns • Surface water exchanges with deeper water in the ocean • Downwelling (surface water sinks) • Upwelling (deeper water rises)

waves

• In deep water, wave orbitals (water motion beneath waves) do not reach the bottom/seabed. • Wave base: depth below waves where water molecules are not affected by wave motion • ~1/2 the wavelength • In shallow water, waves interact with the seabed, slowing and shoaling, and eventually becoming unstable and break

Bathymetric (variation in depth) features include

• Mid Ocean Ridge (MOR)• Trenches • Continental shelves• Submarine canyons• Abyssal plains• Seamounts

types of fossils

• Molds, casts• Carbonized impressions• Permineralized• Trace fossil• Biomarker • Frozen or dried body• Amber or tar• Preserved, replaced parts

oceans

• Oceans cover 70% of Earth's surface • Ocean basins are low-lying lithosphere beneath the sea (lower than continental crust due to isostacy)

fossilization process is influenced by

• Oxygen in depositional environment • Burial rate • Presence of hard part→"preservation potential"

uniformatism

• Physical processes we observe today also operated in the past • "present is the key to the past"

storage and movement of groundwater

• Porosity and permeability of subsurface materials influence rate of movement and amount stored - Porosity = % of total volume of rock or sediment containing pore spaces - Permeability = materials ability to transmit a fluid (ease of flow)

rapids and waterfalls

• Rapids form where water flows over steps or large clasts in the streambed, where channel abruptly narrows, or where the gradient abruptly changes (top right) • Waterfalls form where the gradient of the stream is so steep that some or all water free-falls above the stream bed (bottom right)

James Hutton-geologic time

• Reasoned 1yr to deposit 1 mm of sea sediment, so it must have been millions of years to deposit the thousands of meters of sediment he saw. • Age of Earth MUST be far older than believed • Uniformitarianism - ongoing geologic processes

submergent coasts

• Relative sea level is rising (sea level rising or land sinking or subsiding) - Caused by subsidence of land adjacent to the sea or a rise in sea level • Example:- Atlantic Coast - Features • Estuaries(drowned river mouths)• Highly irregular shorelines

what is a fossil

• Remnants or traces of once living organisms buried and preserved within the sedimentary rock record • Help scientists understand evolution and the history of life; although the record is not complete.

alluvium and stream terraces

• Rise in base level or decrease in discharge can cause a valley to fill with alluvium (fluvial sediment) • A drop in base level or discharge increase will cut down into the alluvial creating stream terraces

angular unconformity

• Rocks tilted or folded before the unconformity developed • Rocks deformed →rocks eroded →new layers deposited

Principle of Lateral Continuity

• Sedimentary rocks • Layers deposited in continuous sheet, then eroded Example: in the Grand Canyon, a single formation can extend over vast areas

Principle of Original Horizontality

• Sedimentary rocks • Layers deposited originally horizontal (then can deform)

principle of superposition

• Sedimentary rocks • Oldest on bottom, youngest on top

streams cut V shaped valleys over time

• Streams cut into underlying strata or sediment forming V-shaped valleys (gently sloping troughs) • Canyon: trough bordered by steep slides- Typical in hard rock • Alternating lithology can form stair-step canyons

running water

• The difference between runoff (surface) and infiltration (underground) depends on - Rain: intensity and duration - Soil type, saturation, amount of vegetation - Slope of the land

Coastal Zone is influenced by several processes

• Tides• Waves• Currents• (& Wind )

natural levees and flood plains

• When water within a river exceeds the channel capacity, or flooding, natural levees and floodplains are deposited. - Natural levees - coarser sediment is deposited along riverbank - Floodplains - finer sediment deposited adjacent to river Note that older deposits record the position of ancient channels and floodplains.

karst landscape

• regions of limestone bedrock dissolution at surface and in cave networks