glaciers Flashcards
what two epochs did the quarternary contain?
- pleistocene- ended about 10,000 years ago
- holocene, began about 10,000 years ago
when was ice at its maximum
-about 20,000 years ago during the pleistocene
what was the name of the less glacial?
-Loch Lomond stadial- ice reached scotland
give en example of a cold period during the holocene
-the little ice age between 13th and 18th centuries
how do milankovitch cycles effect climate change
-obliquity
the tilt angle of the earth, changes every 41,000 years- when tilt angle increases, summers hotter and winters cooler
-precession
earth slowly wobbles on its axis
-changes in solar output
amount of energy from sun varies due to hotspots where radiation is more active than usual. can dissappear for short periods- thought to have triggered the little ice age
apart from milankovitch cycles, what are other causes of climate change?
- the enhanced greenhouse effect- anthropogenic impactcs
- volcanic activity- ash and sulphur dioxide reflecting radiation e.g. 1815, Indonesia, largest wolcanic eruption in human history
what evidence is there of the pleistocene?
- UKs relict landscape, provides evidence that the country was once covered by ice
- depositional features
- erosional evidence
- meltwater evidence
what is permafrost?
- where a layer of sediment, soil or rock below the grounds surface remains almost permanently frozen
- reaches depths of up to 400-500m
- may be continuous, discontinuous or sporadic depending on the temp of the environment
what are the typical characteristics of permafrost areas
- cover about 25% of land area, but in the past their extent was greater
- typically large expanses of featurless land, with blockfields and with marshy, low growing vegetation
- plants include mosses- adapted to living in harsh environments
- thaw lakes are common in the summer. Water is darker, absorbs radiation, increases depth of thawing, creates talik
describe the process of frost heave, in periglacial areas
- upward dislocation of soil and rocks by the freezing and expansion of soil water
- frost push occurs when cold penetrates into the ground
- stones chilled more than surrounding soil, water below the stones freezes and pushes up the stones
- frost pull- alters orientation of stones, causing to stand upright
what is solidfluction
- mass movement of soil and regolith affected by alternate freezing and thawing- can be effected by nivation
- forms solidfluction lobes
give three periglacial landscapes
- pingos
- ice wedges
- patterned ground
what are pingos. describe formation of open system and closed system pingos
-domed shaped hills, 500m diameter, up to 50m in height
-at the core is an ice lens, surface layer usually vegetation. surface may contain cracks due to ground swelling
open system
-water forming the pingo comes from outside the system
closed system
-found at lakes and flat area- continuous permafrost
-e.g. in the mackenzie delta, canada
how are ice wedges formed
- frozen ice within crack in the ground
- ice melts
- more water enters the crack
- freezes, crack expands
- dust and sediment can collect in the crack to form ice wedge molds
how is patterened ground formed?
- as hydrostatic pressure rises, moisture in the ground begins to freeze and rise. forms and ice lens
- capillary action- leads to more moisture joining the ice lens, grows
- lens begins to push stones that are above it- stones have lower heat capacity, so ice lens forms around them7
- smaller sediment filters into the gap left when larger stones are pushed upwards
- stones now poke out of the ground
- ground polygons are formed, patterned ground formed
- stripes form when patterned occurs on slopes
give the characteristics of glacial advance
- equilibrium zone further down the glacier
- snout advance- further reach
- ice is thicker
- moves faster
- there is a positive mass balance
what factors control glacial movement
- gravity- steeper gradient=greater gravitational potential
- friction
- seasons ie. more melting in the summer- negative mass balance
- temerature of ice- temperate glaciers and higher altitudes, lower latitudes- lower temp
- geology- moves faster over impermeable rock
- mass of ice- thicker ice moves faster
what are the processes of glacial movement
- pressure melting point-glacial ice can melt at temps below 0 degrees
- basal slippage- increased friction and pressure at the base
- regulation creep- when glacier meets an obstacle, pressure increases. As stress increases, ice acts like a plastic flows over or around the glacier. less likely at polar glaciers as the lower the temp, the more pressure needed for this to occur
- extending and compressing flow- reduction in gradient, ice decelerates and becomes thicker- erosion greatest here
- surges- may be due to great snowfall in accumulation zone, glacier is out of equilibria
- internal deformation- movement between ice crystals, orientate themselves in direction of flow. cold based move predominantly by internal deformation
what is abrasian
-sand papering effect, occurs because of entrainment-> glacier carries angular, frost shattered material that scours the landscape below
give examples of landforms formed by glacial erosion
- corries
- aretes
- pyramidal peaks
- glacial troughs
- truncated spurs
- hanging valleys
how do corries develop?
- snow collects in a natural hollow- n. facing slopes
- nivation processes causes hollow to deepen
- widen further by abrasian and plucking
- rotational movement scoops out the hollow
give evidence pf rotational movement
-dirt bands that aren’t horizontal, become increasingly angled with depth
what is a glacial trough?
- steep sided, mainly flat bottomed and deep valley
- tend to be straight due to the power and inflexibility of the glaciers that form them
give the formation of a roche moutenee
- glacier moves over penetrating bedrock
- pressure increases, ice melt, meltwater allows allows the glacier to flow over the rock
- upwards part of the rock becomes smoother
- when glacier has moved over the uphill part, pressure decreases and meltwater refreezes to the bedrock
- plucking of the bedrock- leaves cracks in the back of the rock
how is a crag and tail formed?
- area where there is an area of hard rock and softer rock
- resistant rock on the stoss side leaves a steep, jaggered side, and a gently sloping lee side where the ice flows over the less resistant rock
- example is edinburugh castle
give the different types of moraine and what type of feature is moraine?
-ground moraine
-recessional moraine
-terminal moraine
-lateral moraine
-medial moraine
moraine is a depositional feature
what type of features are drumlins and how are they formed
- depositional features
- form in swarms e.g. in Scotland
- drumlin orientation indicates the direction of ice movement
what is a till plain and how is it formed?
- created by the melting of an ice sheet that has become separated from the main glacier
- levels out the topography of the landscape
how is studying erratics useful?
- analysis of the direction of ice movement
- helps created paleo-environments
- can determine origin of the eratic and therefore origin of the ice
give examples of fluvio glacial landforms
- eskers
- kames
- kettle holes and kettle lakes
- outwash plain
how are eskers formed?
- long, winding ridges of sand and gravel
- run parallel to valley sides
- they are casts of sub-glacial meltwater channels- meltwater collects and is highly charged with debris
- when ice melts, sediments in the tunnel settles to form a tunnel
what are delta kames?
-form when a stream deposits material on entering a marginal lake
-what is a kame terrace?
-forms from the infilling of a marginal lake
what is a crevasse kame?
-form when sediment is deposited in crevasses on the surface of a glacier
what is a braided river and where are they found?
- braided rivers are meltwater streams that are choked with sediment
- they are found within outwash plains that are large expanses of sand and gravel that forms infront of the glacier
what are kettle holes and how are they formed
- formed when blocks of ice become separated, deposited
- if conditions right, blocks covered by outwash
- when ice blocks melt, they leave holes in the plain
- water can get in- kettle lakes
give an overview of the Sagamartha national park case study
-the national park is an active glacial landscape
-it is a site of everest, and is a UNESCO world heritage site
Tourism
-footpath erosion, informal footpaths
-water pollution
-waste disposal
-demand for new lodges and hotels
-tourism in Nepal has boosted the local economy–> improved standards of living ie. healthcare, education, sanitation
Climbing Everest
-increased middle class–> adventure holidays
-greater availability to climb as better infrastructure, equipment, better qualified guides
-better weather forecasting
-crowded routes, especially during peak season- litter, pollution
Controls put in place:
-ensure guides must be qualified
-limiting number of permits
-limiting group sizes
how might climate change effect Nepal?
-Nepal particularly vulnerable to climate change
-evidence that the Himalayas are retreating
-decreases in Himalayas impacts hydropower, farming, flooding-avalanches
-increased tourism has led to more deforestation e.g. firewood for fuel, wood for infrastructure
deforestation leads to:
-soil erosion, landslides
-disruption of the water cycle
what projects have been implemented for the management of the sagarmatha NP?
- establishing plant nurseries
- banning goats
- using kerosene- reduce use of fuelwood
- limiting some development projects
give an overview of the Lake District case study
-over 16 million visit each year
-dramatic scenery and well developed facilities
-local economy benefits
-improved services e.g. bus
-money also used to improve environment
-tourism provides 16,000 jobs–> positive multiplier
problems:
-traffic
-air pollution from congestion
-effects transport for locals
-house price inflation
-poorly paid tourism jobs- also seasonal
-footpath erosion
Lake District NP authority- working to improve footpaths
give a case study overview of tourism in Antarctica, how it’s effected by tourism and who owns it
-Antarctica is a vulnerable ecosystem, vulnerable to chnage
-Antarctic Treaty- 45 nations
-members carry out scientific research
-different areas, different nations e.g. large proportion belongs to Russia
-no weaponry testing allowed
-opposition to the treaty e.g. oil companies
Tourism
-increasing
-majority tourism operated by the IAAT- promotes sustainable and environmentally friendly
-tourists educated about importance of the environment
Climate change
-research in Antarctica–> ice cores
-important research for understanding climate change
Mining
-known reserves, mining currently banned
-could change in the future–> access opens up
who are the first nation people in the Arctic?
-the Vuntut people
-north of the Yukon territories in Canada-next to the Alaskan border
-traditional community. Sustainable way of life
-largely dependant on the Porcupine caribou migration
-use the meat, bones for tools and cooking etc. and skin for clothing and tents
the Vuntut used to be nomadic but now sedentary- they have positioned in a strategic place, next to the porcupine caribou migratory pathway.
how is the traditional lives of the Vuntut people being influenced?
opening of the quarry in 2003–> jobs, money, development?
- snowmobiles replaced dog sleds, guns instead of bow and arrow
- younger members moving to find employment- many abandoned traditional lifestyle to work in the quarry or move to the city
what is ANWR and why why is created?
- Arctic national wildlife reserve
- established in 1980 to protect the unique and delicate region above the Arctic circle in Alaska
- the largest wildlife reserve in the USA
- between the Prudhoe bay and the beaufort sea
the trans-alaskan pipeline
-carries oil from Prudhoe bay to the ice free port of valdez
-insulated along its length
-raised off the ground to allow animals to pass
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