Glaciation Flashcards
ICE SHEET SCORING
the action of an ice Sheet / glacier in eroding the land due to englacial till
MORAINE - Lowland depositional landform
Landforms associated with deposition of angular / unsorted till from within, on top or below a glacier
TILL
Unsorted glacial sediment derived from erosion and entrainment of material by glacial movement
TERMINAL MORAINE
Snout of glacier and shows the furthest extent of the advancing glacier
RECESSIONAL MORAINE
Same characteristics as terminal moraine but does not show the furthest extent due to periods of stability allowing a second ridge to accumulate at snout of glacier
GROUND MORAINE
Subglacial till
LATERAL MORAINE
High and almost symetrical ridge formed along the outer edge of glacier and can be several meters high
Medial Moraine
Lateral moraine from two glaciers join, leaving a line of debris in the center to form a low ridge
DRUMLIN
Formed when a glacier moves over moraine in a valley as it cant entrain/erode but smooths top as it travels over. « Oval Shaped Hills»
DRUMLIN - Features
Blunt end facing upstream, gently sloping tail downstream. Usually occur in clusters on flat valley floors or lowland plains in previously glaciated regions
GLACIAL DEPOSITS
- Unstratified
- Unsorted (striations from plucking)
- Angular (physical weathering + erosion)
FLUVIOGLACIAL DEPOSITS
- Stratified (layers due to seasonal variations in sediment accumulation / meltwater discharge)
- Sorted (meltwater loses energy)
- Smooth / Rounded (attrition)
OUTWASH PLAIN
Largest material first as finest material travels furthest along the plain
ESKERS - Ice contact
A curvy ridge of deposited material roughly parallel to valley sides. Discontinuous hills formed by subglacial streams carrying sediments
KAMES - Ice contact
A mount of sediment deposited at the snout of a retreating glacier that form on the ice surface
KAME TERRACE
Ridge on the valley sides resulting from the infilling of a marginal glacial lake
ERRATIC - Lowland Depositional landform
large boulder different to the bedrock it’s on, transported + deposited by a glacier far from origin when the glacier ice melts - give clues to origin of ice and direction of ice movement
Till plain - Lowland Depositional Feature
Created by melting of a large ice sheet detached from a glacier.
Angular unsorted till is often divided into:
- Lodgement till (dropped by moving glaciers)
- ablation till (dropped by stagnant or retreating ice)
Till fabric analysis
the study of the orientation and ‘plunge’ of rock fragments within a till deposit can suggest direction of ice flow at the time of deposition - studies involving 50 or more rock fragments, conducted at several localities, provide glaciologists with evidence of ice-flow patterns - especially in association with other evidence e.g. erratic and drumlin - orientation
What is Pleistocene Glaciation?
Geological period from 2 million years to around 10,000 years ago. 1/3 of lands surface during , whereas currently only 10%
Short term causes of climate change
• ↑ in greenhouse gases enhanced greenhouse effect (agriculture/ industry/ deforestation)
• Changes in the Earth’s reflectivity / albedo effect
• Volcanic Activity - ash clouds (colder - higher albedo) and greenhouse gases (hotter) emitted from the volcano
Long term causes of climate change
• Sunspots - sun isn’t uniform in the amount of energy it releases - 11 year cycle (variations in solar output from sun)
• Milankovitch cycles
Long term evidence of climate change … Antarctic ice cores
bubbles trapped in ice can be assessed for their oxygen isotopes. Ice cores show low CO2 through cool periods + high CO2 in warm periods
Glacial trough - Lower land glacial erosional landforms
steep-sided, flat-bottomed, deep valleys
normally straight due to the power + inflexibility of the glaciers
abrasion through basal slip (plucking also takes place
