Climate Change & Glaciated Landscapes (Edexcel A Level Geography): Flashcards
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Define Milankovitch cycles.
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Define Milankovitch cycles.
Long-term changes in Earth’s orbit, tilt and wobble that alter insolation distribution over tens of thousands of years, driving natural climate cycles.
What is eccentricity in Milankovitch cycles and its timescale?
Eccentricity is the changing shape of Earth’s orbit around the Sun, cycling roughly every 100,000 years, altering seasonal insolation contrasts.
Greater axial increases the contrast between summer and winter, making seasons more .
Greater axial tilt increases the contrast between summer and winter, making seasons more extreme.
What is precession and its approximate cycle length?
Precession is the slow wobble of Earth’s axis, changing the timing of seasons in the orbit, with a cycle of about 26,000 years.
How can small orbital changes lead to large glacial cooling?
Orbital changes cause small insolation shifts, amplified by positive feedbacks like higher albedo from snow and ice, leading to temperature drops of up to about 7\,\text{\degree C}.
Define sunspot.
A cooler, darker region on the Sun with intense magnetic fields, associated with variations in solar output and often with solar flares.
True or False?
Sunspot activity follows an 11-year cycle of highs and lows.
True.
Sunspot numbers rise and fall in a roughly 11-year cycle, altering solar output slightly and influencing climate.
How do large volcanic eruptions affect global climate?
They inject SO2 and ash into the stratosphere, forming sulphate aerosols that reflect insolation and cause short-term global cooling for about 2–3 years.
Define Anthropocene.
A proposed geological epoch in which human activities such as industrialisation and deforestation dominate Earth’s environment and climate, though not yet officially recognised.
The Pleistocene had repeated and periods, each lasting about 100,000 years.
The Pleistocene had repeated glacial and interglacial periods, each lasting about 100,000 years.
True or False?
We are currently living in an interglacial period of the Quaternary.
True.
The present Holocene epoch is an interglacial, with retreating glaciers and higher global sea levels.
What was the Loch Lomond stadial?
A short, severe cold period about 12,700 years BP when glaciers re-advanced in Scotland during an otherwise interglacial climate.
During the Little Ice Age, average temperatures were about to lower than now.
During the Little Ice Age, average temperatures were about 0.5 to 1 degree C} lower than now.
Define cryosphere.
All frozen water parts of Earth, including snow, ice, glaciers, permafrost and sea ice, currently covering about 13% of Earth’s surface.
Where are most cryosphere ice stores found today?
Most cryosphere ice is in Antarctica (about 85%) and the Arctic polar region (about 12%), mainly as ice sheets, shelf ice and permafrost.
The largest single ice mass on Earth is the , an ice sheet up to 4.8 km deep.
The largest single ice mass on Earth is the Antarctic ice sheet, an ice sheet up to 4.8 km deep.
How does the cryosphere create a positive feedback loop in warming?
Melting snow and ice exposes darker surfaces, lowering albedo, increasing solar absorption, causing more melting and releasing carbon and methane, which further warms the atmosphere.
Define Last Glacial Maximum.
A period about 21,000 years BP when over 30% of Earth’s surface was glaciated, sea level was lower and global temperature was about 6°C.
True or False?
The Antarctic is warmer than the Arctic today.
False.
The Antarctic is colder due to strong westerly winds, cold oceans and a large landmass, and is defined by the 10°C January isotherm.
The Arctic polar region can be defined by the Arctic Circle at N or the July .
The Arctic polar region can be defined by the Arctic Circle at 66° N or the July 10°C isotherm.
Define relict glaciated landscape.
A relict glaciated landscape is a landscape formed by past glaciation that remains after the ice has melted, preserving features like arêtes, corries and erratics.
What are glacial striations and glacial polish?
Glacial striations are grooves scratched by larger debris, while glacial polish is the smooth, shiny rock surface created by fine rock flour abrasion.
Hard rocks form steep mountains in glaciated areas, whereas rocks are easier to erode and often found in lowlands.
Hard igneous rocks form steep mountains in glaciated areas, whereas sedimentary rocks are easier to erode and often found in lowlands.
Define pressure melting point (pmp).
The pressure melting point is the temperature at which ice melts at a given pressure; higher pressure lowers the melting temperature of ice.
True or False?
Cold-based glaciers have basal temperatures at or above the pmp.
False.
Cold-based glaciers have basal temperatures below the pmp, so basal sliding is absent and movement is mainly by internal deformation.
Contrast warm-based and cold-based glaciers in terms of movement.
Warm-based glaciers move quickly by basal sliding aided by meltwater. Cold-based glaciers are frozen to bedrock, move slowly and mainly deform internally.
Unconstrained ice masses include ice , and , which are not controlled by surrounding topography.
Unconstrained ice masses include ice sheets, caps and shelves, which are not controlled by surrounding topography.
Define periglacial processes.
Processes in periglacial environments driven mainly by frost action, including ground ice, solifluction, nivation, frost contraction, frost heave and freeze-thaw.
What is pore ice and where does it form?
Pore ice is ground ice forming in the pore spaces between soil and rock particles where meltwater accumulates and freezes.
Thin slivers of ground ice several cm long found in moist soil at night are called .
Thin slivers of ground ice several cm long found in moist soil at night are called needle ice.
How do ice wedges form from frost contraction?
Falling temperatures freeze and contract the active layer, forming cracks that fill with meltwater, which then refreezes and expands into ice wedges.
Repeated nivation processes create depressions known as .
Repeated nivation processes create depressions known as nivation hollows.
What is frost heave?
An upward movement where expanding ground ice and ice crystals forming in soil force soil particles and stones towards the surface.
What landforms can freeze-thaw weathering produce in periglacial areas?
Freeze-thaw creates rough, angular rock fragments forming scree slopes and extensive blockfields (felsenmeer).
Fast solifluction occurs when the active layer becomes and flows downslope, forming characteristic .
Fast solifluction occurs when the active layer becomes heavily waterlogged and flows downslope, forming characteristic lobes.
True or False?
Slow solifluction (soil creep) is driven by repeated freezing and thawing of soil water.
True.
Freezing causes frost heave, lifting particles, and thawing drops them vertically, so over time they creep downslope.
Define permafrost.
Ground where soil or rock has remained at or below 0\text{°C} for at least two consecutive years, often containing ground ice.
What is talik in a periglacial landscape?
Talik is unfrozen ground within surrounding permafrost, which may be open, through, closed, sporadic, or isolated.
True or False?
Periglacial landscapes are mainly shaped by erosion and deposition by glacier ice.
False.
Periglacial landscapes are mainly shaped by freeze-thaw weathering and mass movement, while glacial landscapes are shaped by erosion and deposition by ice.
Define periglacial landform.
A landform created in periglacial environments mainly by frost-action, often associated with permafrost, low vegetation, exposed rock and seasonal meltwater.
Define permafrost.
Ground that remains frozen for at least two consecutive years, often with a seasonal active layer that thaws in summer and refreezes in winter.
Define loess.
A fine, mineral-rich, windblown sediment, often derived from glacial rock flour, forming pale, loosely packed deposits that crumble easily.
What are blockfields (felsenmeer) and how do they form?
They are surfaces covered with angular rock fragments, produced by intensive, repeated freeze-thaw weathering of exposed bedrock in cold, often mountainous regions.
What are solifluction lobes?
Lobed tongues of soil and rock that move downslope when the saturated active layer slides over frozen ground during the summer melt period.
What are terracettes and how are they produced?
Small step-like terraces on slopes, formed by repeated frost heave and thaw of saturated soil, gradually moving material downslope in small steps.
Explain how ice wedges grow over time.
Cracks fill with meltwater in summer, then freeze and expand in winter. Repeated cycles widen and deepen the ice-filled wedge each year.
The ordered pattern of patterned ground forms by the of sediment, stones and ice wedges.
The ordered pattern of patterned ground forms by the sorting of sediment, stones and ice wedges.
What are thermokarsts?
Irregular hummocks and hollows formed when ground ice melts and the overlying material subsides unevenly, often creating marshy terrain.
True or False?
All pingos form in continuous permafrost beneath former lakes.
False.
Closed-system pingos form in continuous permafrost under former lakes, but open-system pingos form in discontinuous permafrost fed by groundwater.
Define the tundra biome.
A cold periglacial biome with permafrost, low temperatures, short growing seasons, no trees over most areas, and low, slow-growing vegetation.
Tundra climates have low precipitation, typically to mm per year.
Tundra climates have low precipitation, typically 150 to 250 mm per year.
True or False?
Trees struggle to grow in tundra because of permafrost.
True.
Permafrost prevents deep root penetration and, combined with strong winds and cold, stops most trees from establishing in tundra regions.
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