GEOG 120 FINAL Flashcards
What is the difference between weather and climate?
Weather is the state of atmosphere at a specific place and time on earths surface
Climate is the long term average values of weather elements such as temperature and precipitation
What are climate normals
Climate trends established for periods of 30 years
What 5 variables influence climate?
Latitude, Seasonality, Air mass circulation, Maritime vs continental, topography
Are temperatures warmer over large continents than adjacent oceans?
yes
What is the difference between airmasses that affect north America in the summer vs winter?
cT - tropical airmass only in summer, cA and cP polar airmasses are smaller
What are the two kinds of climate classification?
Genetic classification - climate classification based on causative factors, like the interaction of airmasses
Empirical classification - based on statistical data such as air temp and precip
What 3 variables does the Koppen climate classification use?
Avg monthly temp
Avg precip
total annual precip
6 major climate groups in KCC?
- A - Tropical (tropical latitudes: no winter season)
- C - Mesothermal (midlatitudes, mild winter)
- D - Microthermal (mid and high latitudes, cold winters)
- E - Polar (high latitudes and polar regions)
- H - Highland (high elevations at all latitudes)
- B - Dry (permanent moisture deficits at all latitudes)
Two points about dry B climates?
- Orographic lifting intercepts moisture-bearing weather systems to create rain shadows along mountain ranges that extend these dry regions into higher latitudes.
- Dry climates are subdivided into deserts and steppes. Both have permanent water shortages, but deserts have greater moisture deficits than steppes.
Three mechanisms of natural climate fluctuation?
- Continental position and topography
- atmospheric gasses and aerosols associated with volcanic activity
- earths orbital cycles
3 Milankovitch cycles
Orbital Eccentricity - variation in the shape of Earth’s orbit influences amounts
insolation; 90,000-100,000 year cycle
- Tilt Obliquity - variations in Earth’s axial tilt increases or decreases seasonal
contrasts in insolation; 40,000 year cycle - Orbital precession - cyclical change in the wobble of the earth on its axis influences seasonal extremes at perihelion and aphelion; 23,000 year cycle
When did the earth form?
4.6bya
What are the two broad earth systems?
Endogenic system - internal processes like plate tectonics, earthquakes, and volcanos that produce flows of heat and material from below crust, radioactive energy is the main energy source
Exogenic system involves external processes that set into motion air water and ice (wind rivers and glaciers) all powered by solar energy
What is the earths core?
Inner + outer core
Inner core is solid iron and nickel - 3200-5200degc above the melting temp but remains solid due to pressure
outer core is molten - flow generates magnetic field
What is the earths mantle?
Lower and upper mantle - 1300c and pressure
Iron and Magnesium
rocks in upper mantle are molten and flow
Boundary between the uppermost mantle and the crust is called the mohorovicic discontinuity
What is the asthenosphere?
uppermost mantle layer of molten rock capable of flowing
40-250km
What is the lithosphere?
layer of crust and uppermost mantle, flow of materials initiates movement of lithospheric plates
Continental vs oceanic crust
Continental crust - 30km thick beneath continents, higher under mountains
silica, aluminium, potassium, sodium, calcium
composted mainly of granite and gneiss
Oceanic crust - 5km thick beneath ocean
silica magnesium iron
composed mainly of basalt and gabbro
What is buoyancy in the context of the crust?
something less dense floats in something more dense, crust floats on denser layers of mantle
where crust load is higher under glaciers or mountains crust sinks into asthenosphere
What is isostasy?
isostatic rebound - movement of the crust
- entire crust is in constant state of adjustment bc of floating up and down
What is the Kola superdeep borehole?
12000m deep, took 20 years, abandoned bc too hot
How do we know wtf is deep in the earth if we haven’t been there?
studying seismic waves and earthquakes
Difference between minerals and rocks, 3 types of rocks?
Mineral - inorganic natural compound having a specific chemical formula and a crystalline structure
Rock - assemblage of minerals bound together or to other materials
- Igneous - fire formed, molten
- Sedimentary - from settling out
- Metamorphic - altered
What are the two most common elements in the crust?
Oxygen and silicon
What are silicate minerals?
from from silicon and oxygen, make up 90% of earths crust
forms primary minerals during cooling of magma
What are igneous rocks?
- derived from molten rock, magma
- magma emerges on Earth’s surface as lava associated with volcanic eruptions
- magma intrudes and cools within crustal rocks; intrusive igneous rocks (e.g., granite)
- slow cooling produces coarse-grained rocks
- magma is erupted as lava and cools on Earth’s surface; extrusive igneous rocks (e.g., basalt)
- rapid cooling produces fine-grained or glassy rock
-mineral composition of igneous rocks; based on the relative contribution of SiO2
* felsic rocks: high %SiO2 – quartz, feldspar - light-coloured minerals; dominate continental crust
➢aluminosilicate minerals
* mafic rocks: low %SiO2 – mica, amphibole, pyroxene – dark-coloured minerals; dominate oceanic crust
➢ferromagnesian minerals
What are sedimentary rocks?
begin as the products of rock weathering (clastic sediments), accumulations of calcareous materials (chemical sediments), accumulations of organic matter
(organic sediments)
- erosion, transport and deposition of sediments
- lithification – compaction, cementation
- both clastic and chemical sedimentary rocks are deposited in layers – strata – that record the environmental history of a region
What are chemically precipitated sedimentary rocks?
formed of thick deposits of mineral compounds that accumulate in marine environments or evaporate from solutions
- limestone forms as calcium carbonate from either marine organisms or carbonate precipitation, cements into thick deposits
- dolomite is a carbonate rock that contains abundant magnesium
- evaporites form in continental locations when minerals evaporate from concentrated solutions
What are organic sedimentary rocks?
Consist of carbon-based materials that accumulate in thick deposits at the surface and then get buried by other sediments
- coal results when the carbon deposits are very slowly compacted, removing water and oxygen, and lithified
- petroleum results when organic deposits are heated so much that they liquefy
- natural gas comes from the remains of microscopic plants that lived in the ocean
* when they died they sank to the bottom of the ocean to decompose, forming gas
What are metamorphic rocks?
igneous and sedimentary rocks are transformed by heating and great pressure to form metamorphic rocks
* rocks become harder and more resistant to erosion
* metamorphism may involve creation of new minerals and/or changes in mineral arrangement
* distinguish between foliated (e.g., gneiss) and non- foliated rocks (e.g., quartzite, marble)
What is the principle of superposition?
Rock and sediment are always arranged with the youngest materials “superposed” toward the top of a rock formation and the oldest materials at the base, if they have not been disturbed; relative age
who is the father of plate tectonics or continental drift?
Wegener
What is plate tectonics?
the theory that the lithosphere is divided into a number of plates that float independently over the mantle and along whose boundaries occur the formation of new crust, the building of mountains, and the seismic activity that causes earthquakes.
*plate tectonic theory describes the motion of Earth’s lithospheric plates.
What are passive margins?
In plate tectonics where continental crust and bordering oceanic crust are
actually on the same tectonic plate and do not move relative to each other
- not geologically active – seismic activity but no active volcanism
What are divergent boundaries in plate tectonics?
divergent boundaries occur in areas of seafloor spreading, where upwelling material from the mantle forms new seafloor and lithospheric plates spread apart in a
constructional process.
Most occur at mid ocean ridges but some occur in continents - great rift valley of east africa
What are convergent boundaries in plate tectonics?
convergent boundaries occur in areas of crustal collision and subduction, where areas of continental and oceanic lithosphere meet, crust is compressed and then lost in a destructional process as it moves downward into the mantle. - ocean-continent collisions
- convergent boundaries form subduction zones, such as off the west coast of South and Central America, along the Aleutian Island trenches, and along the east coast of Japan.
- convergent boundaries also occur where two plates of continental crust collide, such as the collision zone between India and Asia, and where oceanic plates collide, such as along the deep trenches in the western Pacific Ocean.
- similar low densities so neither one sinks, instead they compress and fold and fault
What are transform boundaries in plate tectonics?
Occur where plates slide past eachother horizontally
as they move past they form a type of fault in the crust called a transform fault
- powerful seismic activity
What are volcanoes?
- a mountain or a large hill containing a conduit that extends down into the upper mantle, through which magma and gases are periodically ejected onto Earth’s surface or into the atmosphere
- magma erupted onto the surface is referred to as lava
- most volcanoes are inactive for some time and only erupt when the pressure of the rising mantle material becomes excessive
What are explosive volcanoes and what are they known as?
Composite volcanoes
- Build up over several eruptions
- magma is rich in silica which traps gasses and builds up pressure
- sends volcanic ash and pyroclastic material into air
- composed of lava and pyroclastic sediments
- characterized by steep slopes and small surface area
What are effusive volcanoes and what are they known as?
Shield volcanoes
- fluid eruptions
- far less silica, lower viscosity
- lava flows as rivers of molten rock
- have gently sloping sides
- develop with successive eruptions that gradually build up over a large area
What are volcanic island arcs?
chains of volcanoes that occur at converging or subducting plate boundaries
What is hot spot volcanism?
Area of volcanic activity associated with a stationary zone of an upwelling mantle plume from the asthenosphere
- occurs randomly under continental and oceanic crust
- lithospheric plates move over stationary hotspots
- plate movement can be traced by the evidence of volcanic activity
What is a seamount chain
A string of islands left after being positioned over a hotspot - Hawaii
What is geomorphology?
the science of landforms including the origin, form, evolution, and spatial distribution
What are endogenic processes?
Contribute to the creation of landscapes of high topographic relief, mountains, volcanoes etc
What are exogenic processes?
Contribute to development of landscapes with low topographic relief, plains, sedimentary platforms
What is orogenesis?
mountain building
What is denudation?
Set of processes that transform materials at earths surface
- lowering surface of the continents
- physical and chemical weathering - creates sediments and minerals
- erosion, transportation and deposition - create erosional and depositional landforms
- gravity, running water, wind, waves, ice
What are the two kinds of weathering?
Physical / mechanical weathering - rocks disintegrating without chemicals
Chemical weathering - decomposition due to chemical reactions - ALWAYS in the presence of water
5 factors influencing weathering
rock comp and structure
- climate
- subsurface water
-slope orientation - facing away from sun means more vegetation
- vegetation - plant acid and roots break rocks
do faults and joins increase weathering?
yes, joints are fractures in rock that occur without displacement
3 physical weathering processes
- frost wedging - freeze thaw - when water freezes its volume expands, repeated freeze and thaw can break rocks
- salt crystal growth - crystallization - forms due to moisture, crystals enlarge due to water absorption called hydration - mineral grains are released from rock - granular disintegration
- pressure release jointing - exfoliation - removes overlying rock (pressure release - rocks respond via isostatic uplift (dilation) - expansion results in fracturing to create pressure release jointing
- joints define boundaries of sheet rock - creates exfoliation zones
5 chemical weathering processes
- solution - evaporite minerals - dissolving simple salts in water
- hydrolysis - alumnosilicate minerals - decomposition due to water
- hydration - evaporite minerals - water becomes a part of the chemical composition of the mineral
- carbonation - limestone - addition of carbon
- oxidation - oxygen from water added to minerals, breaks
What are karst landscapes?
regions of limestone or gypsum bedrock characterized by surface depressions (dolines) and well developed solution channels underground caverns created by chemical weathering
- cover 15% of surface
What is regolith?
bedrock that has been weathered and transformed, forms parent material of soils
What is colluvium?
regolith or soil moving on hills due to gravity
4 types of mass movement
Creep - slow process occurring everywhere, under gravity and freeze thaw slowly move downhill
Slide - sudden movement of mass of regolith that is not saturated with moisture - landslide, two forms translational slides and rotational slides (slumps)
Fall - release of rock from a steep slope
Flow - when regolith is saturated with water flows occur, mudflows, earthflow, debrisflow
What are talus cones?
deposits of fallen rock
cones or aprons (many cones)