Physical Geography Unit 3
Terms
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- Lithosphere
- the sold portion of the earth that comes from greek word meaning "rock layer"
- Germorphology
- the systematic study of land forms, their origin, characteristics, and distribution. Focus is on processes which shape the earth
- Topography
- the surface features of a particular place or region
- uniformitarianism
- 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
- Outercore
- similar temperature to innercore, less pressure, and we think it's liquid (molten) iron
- Mantle
- consists of different layers of molten rock; upper layers appear to be a bit more solid and deeper layers more liquid
- Crust
- 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
- rock
- refers to any assemblage of minerals in the solid state. the different mineral combinations account for the myriad of different rock types
- Mineral
- any naturally occurring inorganic substance, usually having a definite chemical composition
- Metal
- 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
- Magma
- 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
- Lava
- 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
- Sediment
- can be moved and spread out across the ground, after being subjected to heat, pressure, and chemical processes
- strata
- 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
- 71%
- land covers ___% of earth
- 29
- 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?
- Mountains
- Subduction
- 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
- Folding
- where rocks are bent
- heavily folded areas appear as?
- series of ridges and valleys
- faulting
- 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
- earthquakes
- 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
- Seismographs
- 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
- Magnitude
- the shaking recorded at a particulr place- and this is a function of both energy and distance from the source
- Focus
- the point underground where the energy causing the earthquake is first released
- epicenter
- 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.
- Volcano
- 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?
- 50
- Hot Spot Theory
- plate tectonic theory that accounts for most volcanoes but not for all
- Hawaii
- 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
- viscosity
- 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
- Tephra
- 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
- Weathering
- 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
- treeroots
- crack rocks in many places
- chemical weathering
- changes in the chemical structure of the rock; water is usually involved
- hydrolysis
- the permanent chemical combination of materials with water producing a new chemical structure which is frequently less resistant to weathering
- oxidation
- involves the chemical combination of minerals with oxygen. metals in rocks and soil literally "rust" and leave rocks easier to break down
- solution
- 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.
- Florida
- 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?
- mudslides
- mudslides
- 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...
- places
- 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
- humus
- 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...
- composition
- soil texture deals with..
- the size of mineral particles; scale runs from coarse materials to fine material
- Gravel
- particles are greatest
- Sand
- particles are second greatest
- Silt
- particles are second smallest
- Clay
- particles are smallest
- loam
- 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...
- texture
- 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?
- erosion
- 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
- relief
- 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
- Bacteria
- 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
- earthworms
- aerate the soil with constant burrowing; improve soil quaity by ingesting and excreting minerals in a form that plants can use
- climate
- 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