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Geography Final Study Set
Chapter 8, Chapter 9, 10
Terms in this set (91)
Geological Time Scale (GTS)
- is a summary timeline of all Earth history
- it names the time intervals for each segment of earths history, from vast eras, periods.
The geological time scale depicts two kinds of time.
absolute time- is the actual number of years before the present.
relative time- is the sequence of events that happened in what order.
Principle of superposition
- to establish relative age based on stratigraphy geologists apply this principle.
- states that rock and sediment always are arranged with the younger beds
- a guiding principle of Earth Science
- the present is the key to the past
for example: if streams carve valleys now, they must have done 500 m.y.a
Along with other planets and the sun Earth is thought to have condensed from a Nebula, of dust, gas, icy comets, about 4.6 billion years ago
the continents had moved together by the end of the Palazeonic era, forming the supercontinent of Pangaea
Wegners Hypothesis, the moving continents slowly plowed across the seafloor in the process of continental drift.
-occurs where plates are colliding. The denser subtracting slab of lithosphere exerts a gravitational pull on the rest of the plate, pulling the plate into the trench.
When rocks are stressed beyond a certain point the strain creates a break or fracture.
Rocks on either side of the fracture move relative to the other side in a process known as faulting.
areas where fractures in the rock demonstrate crustal movement. At the moment of fracture a sharp release of energy occurs producing an earthquake.
Strike Slip Fault ( Transform fault)
forms when rocks are torn by lateral sheering stress.
- the horizontal movement along strike slip fault produces movement that is right- lateral or left lateral depending on the motion perceived on one side of the fault relative to the other side.
- although they do not produce scarps they can create linear valleys such as those along the san andreas fault.
Types of Faults
Normal, Reverse, Strike Slip Faults.
Normal Fault - forms when rocks are pulled apart by tensional stress. When the break occurs, rock on one slide moves vertically along an inclined fault plane.
Reverse Faults- compressional faults associated with converging motion that forces rocks to move upward along the fault plane produce a thrust or reverse fault.
reverse fault- the hanging wall shifts up and over the footwall
Strike Slip Fault
Earthquakes are most often caused
- by fault raptures , but can also be caused by volcanic events.
- The two sides of the fault plane then lurch into new positions, moving distances ranging from centimeters to several meters, release enormous amounts of seismic energy into the surrounding crust.
the subsurface area along a fault plane where an earthquake begins.
The area at the surface directly above the focus.
an after shock may occur after the main shock, sharing the same general area of the epicenter.
A device that records ground movements caused by seismic waves as they move through Earth
Scientists rate earthquakes on-
- either a qualitative damage intensity scale or a quantitive scale that measures the magnitude of energy released.
Mercalli intensity scale
a qualitative scale that uses roman numerals from I to XXI to represent intensities from barely felt to "catastrophic total destruction.
Moment Magnitude scale
-in use since 1993 is more accurate for determining the magnitude large earthquakes than is the ritcher scale.
- considers the amount of fault slippage produced by the earthquake , the size of the surface or subsurface area that ruptured and the nature of the materials that faulted. such as whether they exhibit brittle or ductile characteristics.
a study that examines the history of each plate boundary in order to determine the frequency of past earthquakes.
The eruption type and resulting lava is determined by
- the magmas viscosity. .
Viscosity - is the magmas thickness.
- usually forms on or near the summit. magma rises and collects in a chamber deep below the volcano until the tremendous heat and pressure is sufficient to cause an eruption.
Upward-faulted blocks produced by pairs or groups of faults; characteristic of the mountain ranges of the interior of the western United States.
Pairs or groups of faults that produce downward faulted blocks, characteristic of the interior western United States.
Example- The Great Rift Valley of East Africa, associated with crustal spreading, and the basin and range Landscapes of the American West.
The extremely hot and dense center of the earth, which is believed to be composed of iron and nickel
- At Earths center lies the dense metallic core, divided into an inner core and outer core .
Earth is thought to have condensed from a nebula of dust, gas and icy comets about 4.6 billion years ago.
The core makes up _________ of the Earth's mass.
- one third of Earths entire mass but only sixth of its volume.
The inner core
made of solid impure iron is well above the melting temperature of iron at surface conditions but remains solid because of tremendous pressure caused by the weight of overlaying materials.
The outer core
- molten iron and has a lower density than the inner core.
The rotation of earth
- affects the fluid outer core generating Earths magnetic field.
- above the core lies the mantle a layer of hot but most likely solid material that represents about 80% of Earths total volume.
- the mantle is rich in oxides of iron and magnesium and silicates ,
silicon dioxide- a component of many rocks and minerals.
-Weathering refers to the physical and chemical processes that break up or dissolve rock.
- Physical and Chemical weathering frequently work together.
- weathering does not transport material but rather but simply prepares it for erosion by water, winds and ice - all influenced by gravity
- includes the transport of materials to different locations by moving water, wind, waves, ice, and gravity.
- interaction between the geological forces that uplift land and denudation processes that wear it down represent a continuing struggle between Earths endogenic and exogenic processes.
inclined surfaces that vary with rock structure and climate.
- on every slope, the weathering of rock loosens material for erosio. The slope angle raindrops freezing and thawing animals and wind also promote erosion.
before moving downslope
material must overcome friction inertia
(resistance to movement.) and the cohesion of particles to one another.
a slope is stable if
- its strength exceeds the combined force of gravity and the denudation processes, and unstable if the slopes materials are weaker
Physical Weathering ( also called mechanical weathering)
occurs when rock is broken and disintegrated without chemical alteration.
- By breaking up physical weathering produces more surface area on which chemical weathering may operate.
A single rock broken into eight pieces has doubled its surface area and susceptible to three Primary processes..
- Frost Action , Salt Crystal Growth, and pressure - release jointing.
The result of differential weathering
- often creates spectacular landscapes such as delicate arch shown in the photograph that opens this chapter.
- A cone shaped pile of irregular broken rocks at the base of a steep incline.
- a process where Dry weather draws moisture to the surface of rocks. as the water evaporates dissolved mineral salts in the water form crystals
Forms of Physical weathering
Salt Crystal growth or Salt Weathering.
Different Types of Weathering
Physical and chemical
the movement of surface material, rocks, soil, vegetation propelled downward by gravit.
- can be surface processes or submarine landslides beneath the ocean.
Mass movement materials can range from
dry to wet and involve particles ranging from small to large.
- mass movement can be fast or slow ranging from sudden free fall to gradual to intermittent flows.
All mass movement occur on slopes because
of the downward pulling force of gravity.
Before any sediment moves downslope
- a slope must first exceed the angle of repose. As the driving force in mass movement gravity works in conjunction with the weight, size, and shape of the surface material; the degree to which the slope is oversteepened
The greater the slope angle
the more susceptible the surface material is to mass wasting processes
The resisting force
is the strength of the slope material that is the cohesiveness of its individual particles that work against gravity. Over time all slopes until gravity overcomes friction and slope begins to fail.
In any mass movement
Which of the following is not necessary for well developed Karst to develop?
A discrete area from which all water drains to a common stream.
It is different depends on where you are at the watershed
List the correct sequence of layers in the earth from the surface to the center,
crust, mantle, outer core, inner core
the science of water and its global circulation, distribution, and properties.
Insolation and gravity power the hydrologic cycle and drive fluvial systems.
Individual streams vary gently depending on?
the climate, geology and soils, topography, plant cover.
stream related processes
the area from which a single stream or river and its tributaries drains all of the water
- Define the catchment (water receiving area area of every drainage basin)
form on higher land separating drainage basins often following along ridge tops
every major drainage basin system is made up of ?
- many smaller drainage basins, Each basin gathers and delivers its runoff and sediment to a larger basin, concentrating the volume into the main stream.
A ridge or elevated area that separates drainage on a continental scale,, specifically that ridge in north america that separates drainage to the pacific ocean on the west side from drainage
Steams erode the landscape in three ways
1. headward erosion removes material upslope in the headwaters
2. Downcutting erodes material from the bottom of the stream channel .
3. lateral erosion moves material from the sides of the river.
The difference between anUngraded and graded stream
Ungraded stream- is actively eroding or depositing material in its channel so that its gradient is adjusted to carry the sediment load.
graded steam- has just enough energy to transport its sediment load.
a level below which a stream cannot erode its valley.
- Sea level is the lowest practical level for all erosional processes in most areas.
- not every landscape degrades all the way to sea level.
Temporary local base level
may control the lower limit of local streams for a region.
. The local base level may be a river, a lake, hard and resistant rock, or the reservoir formed by a human made dam.
Facts about local base levels
- In arid landscapes with their intermittent precipitation, valleys, plains, or other low points determine local base level.
Different types of streams
Perennial streams - flow all year which is typical for large rivers and in humid regions with ample precipitation.
Intermittent Streams - flow for several weeks or months each year and may have some groundwater inputs.
Ephemeral streams- flow only after precipitation and are not connected to groundwater systems. Years may pass between flow events.
Exotic Streams - Earths eternal surface system, powered by insolation, which energizes air, water, and ice, and sets them in motion under the influence of gravity.
An example of an exotic stream
The Nile River and the Colorado River
streams carve and shape the landscape the hydraulic action and abrasion.
the squeeze and release action of flowing water that loosens and lifts rocks.
The grinding away of rock by other rock particles carried in water, ice, or wind
meandering streams migrate across their valley bottoms in a sinuous snake like pattern. with distinct flow and channel characteristics.
- these slow moving waters exemplify a low energy stream environment.
Characteristics of a meandering stream
- flow characteristics are best seen in a cross sectional view
- the greatest velocities are near the surface at the center of the channel., corresponding to the deepest part of the stream channel
- velocities decrease closer to the sides and the bottom of the channel because of the frictional drag on the water flow.
-occur when the longitudinal profile of a stream experiences an abrupt change in gradient such as at a waterfall or area of rapids
How nick points result
they result when a stream flows across a zone of hard resistant rock or from various tectonic uplift episodes such as along a fault line.
large stream nickpoints
The general term for the unconsolidated clay, silt, sand , gravel and mineral fragments deposited by running water .
- may accumulate as sorted or semi sorted development.
The process of fluvial deposition occurs
- when a stream deposits alluvium, thereby creating depositional landforms such as bars, floodplains, terraces and deltas.
Flanking many stream channels are flat, low lying areas.
- they are formed by erosion but their surfaces reflect centuries of recurrent flooding and deposition of sediment.
rotational movement of surface material
which of the following are examples of dripstones
The scientific study of caves is known as
which of the following is not a denudation process
Human-induced mass movements produce a category of processes known as
which of the following weather process does not involve water?
Pressure release jointing
Which of the following is not a type of physical weathering process
The maximum angle at which soil sediment, and rock will remain without moving downslope a table slope is
angle of repose.
Rust reformed by the reaction of iron and oxygen in the presence of water is an example of
continuous masses of ice that are much larger than alpine glaciers also known as ice sheet.
Creation of U shaped vs V Shaped valleys.
Recommended textbook explanations
Pearson Earth Science
Essentials of Geology
Dennis G. Tasa, Edward J. Tarbuck, Frederick K. Lutgens
Holt Earth Science
Arthur T. DeGaetano, Jay M. Pasachoff, Mead A. Allison
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