What is a debris flow, and why is one common in a deglaciated valley?

A debris flow is a rapid downslope movement of saturated sediment, and it is common because loose till on steep slopes is easily mobilised by heavy rain or a meltwater surge.

Why does a braided meltwater stream change its channels between seasons?

Discharge varies enormously through the year and the bed is loose sediment, so the stream repeatedly chokes its channels with deposits and cuts new ones.

What happens to a proglacial lake over millennia?

It is progressively infilled by sediment brought in by meltwater streams, eventually becoming a flat area of marsh or farmland.

WJEC A-Level Geography 601-8455-3

Coastal Landscapes

Glaciated Landscapes

Topic overview The glacier as an open system Climate change and the glacier budget Glacier movement Types of ice mass and their distribution Glacial weathering and erosion processes Macro-scale erosional landforms Glacial transport and depositional landforms Fluvioglacial landforms Suites of landforms in glacial landscapes Periglacial processes and ground ice Periglacial action of water and wind Glacial change over different timescales Glacial environments and human activity

Tectonic Hazards

Topic overview The internal structure of the Earth Mechanisms of plate movement Divergent and conservative plate margins Convergent margins and subduction Hot spots and the global distribution of tectonic hazards The hazard profile and measuring magnitude Types of volcano and styles of eruption Primary volcanic hazards Secondary volcanic hazards Impacts of volcanic activity at different scales Contrasting volcanic eruptions Earthquake characteristics and seismic waves Earthquake hazards and ground behaviour Tsunami processes and impacts Contrasting earthquake events Risk, vulnerability and human factors Monitoring, prediction and warning Mitigation, response and the hazard management cycle

Changing Places

Topic overview What gives a place its character Flows and connections that shape places Meaning, perception and attachment to place How places are represented Economic restructuring and the Clark Fisher model Deindustrialisation and social inequality The service economy and its impacts The knowledge economy and clusters Rebranding rural places Managing change in rural places Rebranding urban places Managing change in urban places Comparing a home place with a contrasting place How place change affects people's lives

Water and Carbon Cycles

Topic overview The water cycle as a global system and mass balance Global water stores and residence times Cryospheric processes and sea-level change Drainage basin inputs, stores and outputs Flows within the drainage basin River regimes and their controls Storm hydrographs and hydrograph shape Air uplift, cloud formation and precipitation Excess runoff and flooding Deficit in the water cycle and aquifer recharge The global carbon cycle and its stores Carbon pathways between land and the atmosphere Carbon transfers involving the oceans Carbon stores in biomes and land-use change Changing carbon stores in peatlands Rising atmospheric carbon and its impacts Feedback within and between the water and carbon cycles

Global Migration

Topic overview Globalisation and a shrinking world Classifying and mapping migration Causes of international economic migration Consequences and management of economic migration Refugee movements and internal displacement Rural-urban migration in developing countries Superpowers and global hub cities Migration policy and public debate in the UK Managing refugee crises Informal settlements in developing cities

Global Governance of the Oceans

Topic overview Supranational institutions and global governance Laws and agreements governing the oceans Strategic value of the oceans and maritime security Shipping, cables and illicit flows Sovereignty over ocean resources Managing marine environments Ocean pollution and its management Governance across scales: an ocean case study

EcosystemsContemporary theme

Topic overview The value of ecosystems to people The distribution of global biomes Ecosystem structure, energy flow and productivity Nutrient cycling in contrasting biomes Measuring and threatening biodiversity Conserving biodiversity Succession and local ecosystems The Arctic tundra biome Sustainable use of the Arctic tundra

Economic Growth and Challenge: IndiaContemporary theme

Topic overview India's relief, drainage and climate India's population, society and governance India's resources, hazards and economic geography India's global role and economic growth Environmental pressures of India's growth Sustainable development strategies in India

Economic Growth and Challenge: ChinaContemporary theme

Topic overview China's relief, drainage and climate China's population, society and governance China's resources, hazards and economic geography China's global role and economic growth Environmental pressures of China's growth Sustainable development strategies in China

Development in an African ContextContemporary theme

Topic overview Defining and measuring development Physical factors influencing development Economic factors influencing development Political, social and cultural factors in development The environmental cost of development Desertification Strategies to promote development

Energy Challenges and DilemmasContemporary theme

Topic overview Classifying and distributing energy resources Physical factors in energy supply The changing demand for energy Managing oil and gas globally Problems of extraction, transport and use Energy mixes and development Sustainable solutions to energy demand

Weather and ClimateContemporary theme

Topic overview Structure of the atmosphere and the heat budget Global atmospheric and oceanic circulation The world's major climate types Weather and climate of Wales and the UK Extreme weather and ENSO Hazards of low and high pressure systems Urban climates and air quality People, climate and the future

Fieldwork and Geographical Skills

Topic overview The six-stage enquiry process Sampling and data collection Presenting geographical data Statistical analysis of geographical data Fieldwork techniques and apparatus Map skills: grid references, latitude and longitude, scale and direction

Key Concepts in Geography

Topic overview Systems, equilibrium and feedback Causality, interdependence and mitigation Resilience, risk and sustainability Place, space, scale and representation

Glaciated Landscapes

Glacial change over different timescales

3 things to know
AS Unit 1

Overview

Glacial landscape changing within seconds, debris flow and seasonal change in fluvioglacial deposition.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Describe the seasonal change in fluvioglacial deposition.

Key term

Give an example of a glacial landscape changing within seconds.

Key term

Why are glacial trough walls prone to sudden failure after the ice has gone?

Questions from this subtopic

Each one with the model answer underneath.

1
Give an example of a glacial landscape changing within seconds.
Model answer
A rock fall from an over-steepened trough wall, which can remove tonnes of material from the valley side in moments.
2
Why are glacial trough walls prone to sudden failure after the ice has gone?
Model answer
The ice was buttressing them, so its removal leaves the steepened rock unsupported and it fails once weathering opens the joints.
3
What is a debris flow, and why is one common in a deglaciated valley?
Model answer
A debris flow is a rapid downslope movement of saturated sediment, and it is common because loose till on steep slopes is easily mobilised by heavy rain or a meltwater surge.
4
Describe the seasonal change in fluvioglacial deposition.
Model answer
Summer melting greatly increases discharge, so streams carry and deposit far more sediment on the sandur, while winter flow is low and little is moved.
5
Why does a braided meltwater stream change its channels between seasons?
Model answer
Discharge varies enormously through the year and the bed is loose sediment, so the stream repeatedly chokes its channels with deposits and cuts new ones.
6
What happens to a proglacial lake over millennia?
Model answer
It is progressively infilled by sediment brought in by meltwater streams, eventually becoming a flat area of marsh or farmland.

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Coastal Landscapes

Glaciated Landscapes

Tectonic Hazards

Changing Places

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Governments must win votes.

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AFew coastal people recognised the signs.

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