EV203 CUM TEE

How does Koppen classify climates?

three letter systems where the first letter is the major climate group, the second is precipitation patterns, and the third is temperature patterns

A climates

tropical humid: low latitude (equatorial), warm (insolation), wet (ITCZ)

B climates

dry: deserts and steppes (subtropical and midlatitude for both)

C climates

mild midlatitude: mild winters (includes Mediterranean, humid subtropical, and marine west coast)

D climates

severe midlatitude: severe, cold winters (includes humid continental and subarctic)

E climates

polar: high-latitude cold climates (includes tundra and ice caps)

H climates

highland: altitude is the dominant control, only in high elevation areas

Second letter A, C, & D climates

f - wet and warm all year; largest control is latitude
m - monsoon pattern; largest control is the monsoon season
w - winter dry season - largest control is ITCZ
s - summer dry season

Second letter B climates

w - desert
s - steppe
both controlled by subsidence from subtropical highs, cool ocean currents, and rain shadows over mountains

Second letter E climates

T - tundra
F - ice cap

Third letter C & D climates

a - hot summers
b - warm summers
c - cool summers
d - very cold winters

Third letter B climates

h - hot desert or steppe
k - cold desert or steppe

proxy

substitute measures of climate to reconstruct conditions in the past

six climate proxies

dendrochronology, oxygen isotope analysis, ice cores, palynology, glacier landforms, speleothems

dendrochronology

dating past events by analyzing tree rings; usually one ring is added per year, and wider rings indicate more growth and nutrients

oxygen isotope analysis

the ratio of oxygen 18 to oxygen 16 in the molecules of substances such as water and calcium carbonate can tell us about the environment in which those molecules formed

ice cores

they can be studied for oxygen analysis and direct information of what is in the ice and how it is structured, which can sometimes preserve ancient environmental evidence

palynology

airborne pollen from trees and other plants can be preserved in sediment layers on lake bottoms and in bogs, which can be used for radiocarbon dating

glacial landforms (for climate proxies)

glaciers leave distinct marks on a landscape by scratching and polishing bedrock on valley walls; mounds of moraines (unsorted glacial rock) accumulate at the edges of glaciers

speleothems (climate proxy)

deposits that form slowly as mineral-rich water drips into cave openings (forming stalactites and stalagmites)

four causes of climate change

atmospheric aerosols, fluctuations in solar output, variations in Earth-Sun relations, and greenhouse gas concentrations

atmospheric aerosols

large quantities of particulates ejected into the atmosphere by volcanic eruptions/asteroids (natural) which can cause ash to circle the earth in the stratosphere and block solar radiation; sulfates/black carbon (anthropogenic) can both heat and cool the atmosphere

fluctuations in solar output

sunspots can occur which reduce solar energy which can cause changes in solar output; these are natural and change back and forth over time

variations in Earth-Sun relations

Milankovich cycles
earth's eccentricity (shape of orbit) varies in cycles every 100,000 years
earth's obliquity (tilt) varies in cycles every 41,000 years
earth's procession (wobble) varies in cycles every 25,800 years
all of these are natural

greenhouse gas concentration

increased greenhouse gases trap more heat within earth's atmosphere; usually anthopogenic

NPP \= PLT

net primary productivity is aided by precipitation, light, and temperature

light for plant growth

green plants need light to survive and conduct photosynthesis

moisture for plant growth

this factor most influences the patterns of living organisms; organisms adapt to the amount of water they receive

temperature

species are best able to survive in areas of moderate or warm temperatures; many cannot survive when it is too cold

biome

a collection of plants and animals over a large area that has broadly similar adaptations and relationships with the environment and climate; major ones include forest, savanna, grassland, desert, and tundra

tropical rainforest

high rainfall and relatively high temperatures (usually Af and sometimes Am); high biodiversity; very shady under tree canopy with windless air, warmth, mold, and decomposition; equatorial

tropical deciduous forest

high temperatures year round but seasonal rainfall (usually between Af and Aw climates); canopy is not as thick or consistent so there is more ground growth; located in the tropics

tropical scrub

low-growing, scraggly trees and tall bushes, usually with a lot of grass (drier portions of Aw and BSh); less biodiversity; a lot of ground-dwelling animals; further poleward than tropical deciduous forests

tropical savanna

tall grasses and seasonal rainfall (Aw); biodiversity varies, but in Africa this is where "big-game" live; grass is green during rainfall and brown in drought

desert

regions in the subtropics that receive little to no rainfall (BWh and BWk); there are some shrubs and succulents (xerophytic plants); faunal life usually moves at night; lack of NPP because of high pressure

mediterranean woodland and shrub

located in scattered midlatitude areas; have dry summer, wet winter precipitation typical of Cs climates; woody shrubs; fires in summer

midlatitude grassland

widely in North America and Eurasia includign BSh and BSk climates; prairie grasses are common; most plants are perennials

midlatitude deciduous forest

very common in northern hemisphere; most has been removed for crop farming; dense growth of tall trees with interwoven branches that form a canopy; forest floor is barren; richest midlatitude fauna

boreal forest

aka the taiga; vast in North America and Eurasia; close to Dfc climate; commonly evergreen trees and some deciduous trees; some soil remains frozen throughout the year; more growth at lower latitudes; fauna is limited

tundra

cold, arid grasslands in which moisture is scarce and summers are so short and cool that trees cannot survive; some grasses and shrubs

andisols

parent material dominated; soils from volcanic ash and prevalent in volcanic regions; usually new and unweathered; andi \= ashey

gelisols

climate dominated; young soils that develop slowly because of cold conditions, typically in a permafrost layer; g \= glacier

histosols

site dominated; organic soils that are saturated with water and located in high-latitude regions that experienced glaciation; contain undecayed matter or masses of muck because of a lack of oxygen

aridisols

climate dominated; soils of dry lands without water to remove soluble minerals from the soil; sandy, dead, and dry desert soils; arid environments

vertisols

parent material dominated; located in alternating wet/dry climates; large quantity of clay that swells and cracks as it absorbs water and then dries; no vertical construction

mollisols

climate dominated; contains abundant humus and remains soft when dry; most productive soil order; m \= most productive

oxisols

time dominated; displays a high degree of mineral alteration and profile development; impoverished tropical soils without nutrients

driving mechanism for plate tectonics

deep convective currents within the mantle drive magma to the surface creating new ocean seafloor; newest seafloor is near midocean ridges

Earth's crust

outermost shell; broad mixture of rocks that make up 1% of the volume and 0.4% of the mass of the earth

continental crust

around 70km deep and made of less dense and heavy rocks

oceanic crust

around 7km deep and made of denser and heavier rocks

Earth's mantle

beneath the moho, it is composed of high-density rock that extends down to a depth of approximately 2900km that makes up 84% of the volume and 2/3 of the mass of the earth

upper mantle

thin and rigid; 65-100km; this and the crust forms the lithosphere

asthenosphere

beneath the rigid layer of the lithosphere to 350km, rocks become hot and plastic like tar

lower mantle

beneath the asthenosphere, rocks are very hot but less plastic because of the pressure

Earth's cores

made of iron/nickel or iron/silicates; makes up 15% of the volume and 32% of the mass of the earth

outer core

beneath the mantle is the molten outer core, extending to around 5000km

inner core

innermost portion of the earth; solid because of high pressure; radius of 1450km

felsic igneous rocks

light-colored, less dense, high viscosity, high silica content, continental

mafic igneous rocks

dark-colored, more dense, low viscosity, low silica content, oceanic

endogenic processes (internal)

originate from within the earth; generally processes that build up

exogenic processes (external)

originate from the atmosphere; generally processes that break down (WMWE)

Wegener's evidence

paleontology: same plants and animals on different continentsmountain ranges: different continents' mountain ranges seem to fit togetherrock deposits: same rocks and rock developments in different continentscontinental puzzle: continents appear to fit together

Theory of Plate Tectonics

theory that earth's lithosphere is made of large plates that have been moving for 3.4 million years

evidence for plate tectonics

vast chains of underwater volcanoes (seamounts), seafloor spreading, and seafloor subduction

three plate boundaries

divergent, convergent, transform

divergent boundaries

magma from the asthenosphere rises between two places which causes upward upward flow of molten material; constructive; red line on map

types of divergent boundaries

midocean ridges and continental rift valleys

midocean ridges

oceanic divergent boundaries at active or extinct spreading ridges because of shallow-focus earthquakes; new crust is formed

continental rift valleys

continental divergent boundaries

convergent boundaries

destructive boundaries where mountain ranges, volcanoes, and ocean trenches occur; most orogenesis starts here; black line with small triangles on a map

oceanic-continental convergence

dense oceanic lithosphere underrides continental lithosphere when the two collide; magma penetrates the less subductive plate and form a volcanic mountain range; the subductive plate goes down and forms a trench

oceanic-oceanic convergence

the more dense plate subducts beneath the less dense plate; creates trenches between the plates and volcanic island arcs on the nonsubductive plate; earthquakes usually happen

continental-continental convergence

no subduction takes place because the crust is too buoyant; giant mountain ranges form

transform boundaries

two plates slip past one another laterally and do not create or destroy landmass; often cause seismic activity and occur on midocean ridge systems; yellow line on map

denudation

the overall effect of the disintegration, wearing away, and removal of rock material; includes WMWE

weathering

breaking down of rock into smaller pieces by atmospheric and biotic action

mass wasting

the relatively short-distance downslope movement of broken rock material under the direct influence of gravity

erosion

the removal, transportation, and deposition of fragmented rock material over wider areas and sometimes greater distances than is the case for mass weathering

mechanical (physical) weathering

physical disintegration of rock material without any change in its chemical composition; common in cold, dry climates

types of mechanical/physical weathering

frost wedging, salt wedging, temperature changes, exfoliation

frost wedging

most important agent of mechanical weathering; repeating the freeze-thaw cycle, usually in D climates

salt wedging

occurs when salts crystallize out of solution as water evaporates; these crystals grow and split rocks, often in B and coastal climates

chemical weathering

decomposition of rock by chemically altering its minerals; it happens after mechanical weathering exposes rock to this; requires the presence of water; common in warm/moist climates

types of chemical weathering

oxidation, hydration, hydrolysis, carbonation, spheroidal

oxidation

oxygen atoms combine with atoms of metallic elements in minerals, creating new products that are more voluminous, softer, and easily removable

carbonation

carbon dioxide and water combine to form carbonic acid, which reacts with carbonate rocks producing calcium bicarbonate, which is then easily removed by water runoff (dissolution)

climate and weathering

chemical weathering is enhanced by warm/moist environments, which causes more weathering to occur in tropical regions instead of arid ones

mass wasting events

rockfalls, landslides, slumps, earthflows, mudflows, and creeps

rockfall

pieces of rock falling downslope; dry conditions; rapid movement; often resulting from frost wedging

landslide

slope failure where a slope collapses and moves along a generally flat sliding plane; moderate moisture; rapid movement; leaves a scar with debris

slump

slope failure where rock or regolith moves downward and rotates outward along a curved sliding plane that is concave up; moderate moisture; slow movement

earthflow

when a water saturated slope moves partially downhill after a heavy rain; high moisture content; slow movement; causes a bulging lobe of material at the bottom

mudflow

originates in drainage basins when a heavy rain - often following a long dry spell - produces a cascading runoff too great to be absorbed; high water content; very large movement; large debris; no slope failure

creep

gradual downhill movement of regolith so unobtrusive that it is recognized by indirect evidence only; slowest moving; involves temperature and precipitation patterns

deposition

transported material set down in another location

straight stream channels

straight and short; uncommon in nature; controlled by geologic structure (jointing and faulting); human-made channels (urban and canals)

sinuous stream channels

sinusoidal, winding channels; usually surrounded by steep mountains

meandering stream channels

twist and turn back on itself; in flatlands; fine-grained suspended load; typically old streams; continuous process of erosion and deposition

braided stream channels

multiple interwoven and interconnected channels; flat stream channel with heavy sediment load; common in alpine areas (glacier meltwater) and arid areas (periods of low stream discharge)