climate - droughts, deserts, glaciers

what is a driver of desert formation

precipitation

kinds of deserts

sub-tropical, coastal, continental-interior, polar

sub-tropical

1) hot, moist air rises into atmosphere 2) as air rises, it cools and drops into moisture as heavy tropical rains 3) air that moves away is cooler and drier 4) as air masses approach sub-tropics, air descends and warms up again 5) descending air hinders formation of clouds, so little rain falls

coastal deserts

1) warm air rises from warm surface 2) cold ocean currents make surrounding air at land surface cold 3) coastal areas near cool ocean currents are cold and do not have a lot of rain clouds

continental-interior deserts

1) a lot of moisture on the continents comes from the ocean 2) by the time moisture laden clouds rain on coastal areas, air traveling inland has lost moisture and does not rain everywhere 3) leads to inland deserts

polar deserts

most of the water is locked away in ice (unavailable to organisms) and very little precipitation happens in general

water erosion

when it does rain in deserts, landscape is rapidly changed

wind transport

bigger grains are eroding the surface, smaller grains are picked up into the wind

differential weathering

different rocks are more or less resistant

droughts

combination of high temperatures and low precipitation

what led to dust bowl

high temperatures, low precipitation, inexperienced farmers, unsustainable agricultural practices

future of droughts

more intense (less rainfall, extreme heat), longer, more frequent

how to help droughts

collaborative efforts, watershed sustainability, long-term monitoring of impacts

conditions for glacier formation

cold, lots of snow, gentle slopes, snow protected

cold

climate must be cold enough that winter snow doesn’t entirely melt away during summer

lots of snow

must be enough snowfall for a large amount of snow to accumulate

gentle slopes

surface where snow accumulates must have a gentle enough slope that snow falling on it doesn’t slide away in avalanches

snow protected

area where snow falls must be protected enough that snow doesn’t blow away

zone of accumulation

where rain/snow falls and accumulates as ice

zone of ablation

where parts of the glacier are going away

sublimation

process through which solid becomes gas (doesn’t transform into liquid)

glacial advance

when there is more accumulation

glacial retreat

when there is more ablation

ice age

period of cooling that allows permafrost and glaciers to advance

how to figure out extent of past ice ages

as they advance/retreat, glaciers leave behind striations

when there is no glaciation, stream carved landscapes are in a

V shape

when areas experience conditions to form glaciers

V shaped valleys fill with ice

after glaciation, region contains

U shaped valleys

indications of past glaciation

observing striations and U shaped valleys

long term causes for ice ages

plate tectonics, carbon dioxide

short term causes for ice ages

eccentricity, axial tilt, precession, albedo

eccentricity

changes to the earth orbital shape

axial tilt

different tilt angles can change amount of radiation absorbed

precession

earth wobbles, which also affects the solar radiation absorbed

albedo

high albedo surfaces reflect sunlight and radiation, leading to earth cooling