Glossary of Physical Geography Unit 3

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the sold portion of the earth that comes from greek word meaning "rock layer"
the systematic study of land forms, their origin, characteristics, and distribution. Focus is on processes which shape the earth
the surface features of a particular place or region
based on the assumption that physical processes active in the environment today have been operating at the same place and intensity throughout gelogic history
Topographic features
they can change rapidly while others can take a long time
geologic time
far different than time for people. we think earth is 4.6 billion years old
Geologists have broken down history into what?
eras, periods, and epochs
Holocene Epoch
the past 10,000 years since the end of the most recent ice age
Pleistocene Epoch
covers the 1.65 million years, just prior tot he HOlocene
Inner core
several thousand degrees C, but under so much presser, we think it is a solid chunk of iron
similar temperature to innercore, less pressure, and we think it's liquid (molten) iron
consists of different layers of molten rock; upper layers appear to be a bit more solid and deeper layers more liquid
the upper most layer of solid rock. 3 to 43 miles thick
seismic waves
affected by variations in temperature, presure, density, structure and composition of the materials of the different layers of earth which have been studied to find out all about the earth's structure even though holes were not dug deep enough
refers to any assemblage of minerals in the solid state. the different mineral combinations account for the myriad of different rock types
any naturally occurring inorganic substance, usually having a definite chemical composition
special class of minerals found in rocks, inorganic, but malleable and conduct electricity
3 major types of rocks
Igneous, sedimentary, metamorphic
Igneous Rocks
formed directly from liquit state and cover about 1/3 of earth's land area
molten rock below the earth's surface
Intrusive igneous rocks
when magma squirts through the cracks in the crust but stops moving before reaching the surface (cooling slowly); more resistant to erosion
when magma appears at the earth's surface
extrusive igneous rocks
when lava spreads across the earth's surface (cooling much faster); these rocks break down more quickly
Sedimentary rocks
formed when rocks are broken down into smaller particles called sediment; cover almost 2/3 of earth's land surface
can be moved and spread out across the ground, after being subjected to heat, pressure, and chemical processes
several horizonal layers that are relatively soft and pliable
clastic sediments
inorganic rock fragements (sandstone)
chemical sediments
formed by the preciptation of mineral materials out of water
organic sediments
produced from remains of plants & animals... many are associated with animal shells
metamoprhic rocks
either igneous or sedimentary rocks that have been changed by some combination of heat and pressure; least prevalent of the three basic rocks; usually associated with mountain building processes
ocean covers ___% of earth
land covers ___% of earth
what makes up the ocean's floor?
the crust of continents consits of less dense materials than the crust
What will happen if ocean drops 350 feet?
it will expose an additional 5-6% of land surface, coresponding tot he continental shelf
Alfred Wegener
proposed that present continents originated as a single land mass called Pangea which begain drifting
What was the problem with Alfred's theory?
he could not satisfactorily explain the mechanism that caused the movement in the crustal plates
Tectonic activity
refers to all forms of breaking & bending of crust; comes from a greek word meaining "building"
Plate tectonic theory explains what?
the location of volcanoes and earthquakes, the distribution of mountain ranges and other major structural features of earth's surface
earth's crust is comprised of several relatively rigid but fragmented what?
plates that move relative to one another by floating or gliding across the relatively plastic mantle below
how often to the plates move?
inches per year
What drives plate movement?
earth scientists believe it is due to the heat currents in the earth's interior
Divergent plate boundaries
where plates move apart from each other and magma moves up to take the place of the two plates that are separating
where are divergent plate boundaries located?
beneath the world's oceans where the zone of divergence features not only spreading but also vertical development
since the thickness of ocean floor sediments increases with increasing distance from the rift itself this indicates what?
that those areas near the rift are geologically younger
Transform plate boundaries
boundaries where plates slide past each other
east africa's rift valley
zones of divergence resulting fragmented trench is loaded with tall volcanoes and perhaps the eastern part will eventually split away from the rest of the continent
Are there volcanoes along transform plate boundaries?
No, but earthquakes are common
Because of the transform plates, what will happen to california in the future?
Los Angeles will eventually rest aside San Fransisco
Convergent plate boundaries
where plates collide head on and this can produce two different results.
head on collisions between plates of similar desnity can result in?
a process where a denser oceanic plate runs into and dives under a less (continental) plate
subjection often leads to?
trenches off shore and volcanoes on shore
where rocks are bent
heavily folded areas appear as?
series of ridges and valleys
associated with the cracking, breaking and fracturing of rocks under pressure
most major faults extend into the ground and?
may or may not be clearly visible at surface
the shaking & trembling of earth's surface associated with crustal movements
95% of earthquakes are where?
pacific rim, southern europe and Southern asia
scientists do not have a complete understanding of earthquakes because...
there are occasional seriously earthquakes far from plate boundaries
delicate instrument that detects earthquakes
Seismic Activity
the movement that is detected by seismographs
Sudden movement of earth materials sends....
shock waves through the earth
the further away you are from the source...
the more that energy is dispersed over a large area, and the less likely you are to experience motion or damage
the shaking recorded at a particulr place- and this is a function of both energy and distance from the source
the point underground where the energy causing the earthquake is first released
the point on the earth's surface drectly above the focus of an earthquake
Earthquakes can occasionally alter ? and are harmful to ?
land forms; structures we build
Moment Magnitude Scale
the earthquake intensity scale that was devleoped by Charles Richter...goes up to about 8 or 9 in rating; as magnitude increases, they become less frequent
Forecasting earthquakes
theory focuses that statement a little by suggesting that the longer the period is since an earthquake has occurred, the more likely that place is to experience a quake.
is a mountain or vent in the earth through which flows molten rock and gas
Why does magma come up to surface?
the density of magma is less than that of the rock from which it melts
80% of all active volcanoes are associated with?
the pacific ahuge zone of fire
The Cascade Mountains
running from northern california, through oregon and into washington have several volcanoes
Alaska's ? are a series of volcanoes
Aleutian Islands
About how many volcano erruptions per year?
Hot Spot Theory
plate tectonic theory that accounts for most volcanoes but not for all
rests squarely in the middle of the pacific plate and are part of a long arc of volcanic mountains trending northewest to southeast
Islands at the northwest end of the chain are?
older and more worn down
Kauai is how old?
5 million years
Oahu is how old?
2 to 3 million years
Big Island of Hawaii is how old?
less than a million years old and has active volcanoes
Eruptions featuring little gas...
are usually less explosive than eruptions featuring a larger % gas
if Magma rises slowly there is...
a greater opportunity for compressed gases to react to changed pressure and escape without generating a significant explosion
if magma rises quickly to the surface...
the rapid pressure change causes gases to expand suddenly leading to a violent explosion
a function of magma temperature
hot magma
more liquid and less viscous and it dissolved gases easily come out of solution when magma surfaces-therefore eruptions are less likely to be violent
cooler magma
is more viscous; this inhibits the release of compressed gas which builds and frequently causes violent explosions
gas, ash, steam, and large rock fragments produced by volcanoes
Pyroclastic flow
all the tephra matierals that may move downhill
Eruptions can be brief, lasting hours or less but...
last for decades at a time
large areas may become blanketed with thick layers of ash, which may become a ?
mudslide after a heavy rain
on occasion, geoscientists can obtain data that help them accurately predict an eruption, but other times, violent eruptons provide no
warning of any kind
the combined action of physical (mechanical and chemical processes that break down rocks); is essential in producing soil
Physical or mechanical weathering reduces rocks without...
changing their chemical composition
joint and fracture formation
caused by tectonic forces and rapid cooling; they create more pathways for weathering agents to continue the process
frost wedging
occurs when water makes its way into joints or fractures in rocks and then freezes
salt crystal growth
in dry environments, high rates of evaporation leave behind salts to collect in cracks
crack rocks in many places
chemical weathering
changes in the chemical structure of the rock; water is usually involved
the permanent chemical combination of materials with water producing a new chemical structure which is frequently less resistant to weathering
involves the chemical combination of minerals with oxygen. metals in rocks and soil literally "rust" and leave rocks easier to break down
occurs when certain materials literally dissolve in water; water can dissolve carbon dioxide and this carbon in this water can combine with certain matierals that can be dissolved and carried away
Karst topography
the distinctive surface features, which are the direct and indirect result of solution by water
karst landscapes
most often found in humid places underlain by limestone, which is easily dissolved
caverns are left behind when...
water sinks into the ground and after carbonation/solution empties
caverns can collapse creating...
sinkholes and if deep enough can turn into lakes if the base is below the water table
what is one of the leading places for karst topography in the U.S.
chemical weathering operates best in
warm teperatures where water is present, warm and rainy climates are espeically vulnerable to chemical weather. Also, chemical processes break down rocks much faster
mass movement
the down slope movement of surface material by gravity
angle of repose
used to describe the steepest angle that something can endure before falling. the exact value depends on the type of material and the condition of the surface.
slow mass movements
generally are imperceptible but may take days, weeks, or even years to happen but are more prevalent and they move more material than more rapid mass movements
rapid mass movements
characterized by perceptible movements of materials but are usually brief and potentially dangerous; they are not shapers of the large portions of the earth's surface
where do rapid mass movements occur?
mountains or hilly places
where do slow mass movements occur?
in humind environments
what is the most fluid major type of land movement?
more often an arid climate phenomena and usually triggered by heavy rain; generally long and narrow, frequently occuring in or around the normally empty channels of dry riverbeds
rock or land slides
the general term for al other forms of rapid debris flows
soils of different properties are produced in different...
soil composition
mineral or inorganic content that comes from weathered rock
all soils have at least some..
water even if it's nothing more than a microscopic layer around each grain; this is important because this is what dissolves minerals that plants depend on
all soils (except those saturated by water) contain...
air; maybe not enough for us to breathe but enough for plants,small animals, and microorganims
organic material
comes from both decomposing plant and animal material as well as living organisms
partially decomposed plant remains; is a source of nutrients to living plants; spongy consistency of humus increases soil's water retntion capactiy; helps resist erosion
a soil's color provides clues as to it's...
soil texture deals with..
the size of mineral particles; scale runs from coarse materials to fine material
particles are greatest
particles are second greatest
particles are second smallest
particles are smallest
when soil have relatively an even percentage of all three particles; occupy an intermediate position in terms of water rention and are preferred for agriculture
a soil's ability to retain water is determined by it's...
sandy soils
allow water to move through them too quickly and may require irrigation to cultivate
fine textured soils
prevent the movement of water through them; they may retain too much water or completely prevent water from penetrating to deep layers
structure of soil
a mesasure of how well a soil hangs together or clumps
What provides soil structure?
organic materials, moisture, and texture
structure helps prevent what?
fine textured materials with organic materials may have too much structure and be...
difficult to work with
soil profiles
vertical slices of soils
soil horizons
differnt layers of soil
Parent material
the inorganic material that forms the basis of most soils
residual materials
parent materials from underlying bedrock that dominate a soil
transported materials
may have been orginated from away and then been deposited
vertical characterization of a landscape
soils on steep slopes
tend to be thinner and consist of more coarse material because they are easily eroded; also more likely to be dry because course texture allows moisture to escape
soils in flatter places
tend to be thicker and much better developed
depressions on the landscape
are more likely to have waterlogged soils because they are the destination for many fire textured materials
the most numerous critters in almost any healthy soil; produce organic acids that break down parent material creating more soil; help decompose dead plants and animals
Nitrogen fixation
converting atmospheric nitrogen into a form that plants can use
vascular plants
prevent soil erosion after heavy rain
plants die and serve as a source of...
nutrients for living plants
trees with deep roots
pump nutrients from deep layers in the soil up to the surface where they can be recycled as leaf litter
aerate the soil with constant burrowing; improve soil quaity by ingesting and excreting minerals in a form that plants can use
preciptiation may cause leaching of important minerals beyond the root zones of many plants
dry places
excessive evaporation may leave behind so many dissolved minerals over time that soils become salty
cool climates
frequently have more acid soils because cool weather retards the decomposition of organic materials
soils can be thought as a renewable resoure because
it accumulates over time
soils have ben divided into..
several types and soil maps reflecting the variety of different soil types that have been produced

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