Key Terms

📖 Key Terms

Igneous rock

Rock formed from cooled and solidified magma. Intrusive igneous rocks (e.g. granite) cool slowly underground and have large crystals. Extrusive igneous rocks (e.g. basalt) cool quickly at the surface and have small crystals. Both types are hard and resistant to erosion, forming upland areas in Britain.

Metamorphic rock

Rock that has been transformed by heat and/or pressure from its original state. Existing rocks (igneous or sedimentary) are recrystallised into harder, more compact forms. Slate (from mudstone) and schist (from various parent rocks) are the most common metamorphic rocks in the UK.

Sedimentary rock

Rock formed from layers of sediment (particles, shells, or chemical precipitates) that are compressed and cemented over millions of years. Generally softer and less resistant than igneous or metamorphic rocks. Limestone, chalk, and clay are the dominant sedimentary rocks in lowland Britain.

Watershed / drainage divide

The boundary between two drainage basins — the high ground from which precipitation drains to opposite sides. In England, the Pennines act as the main watershed, with rivers draining east to the North Sea and west to the Irish Sea.

Drainage basin

The area of land drained by a river and all its tributaries. All precipitation that falls within the drainage basin eventually flows into the main river. Drainage basins are separated from each other by watersheds.

Glaciation

The process by which glaciers and ice sheets shape the landscape through erosion (plucking and abrasion), transportation, and deposition. Most of Britain's dramatic upland scenery was shaped during the last Ice Age, which ended approximately 12,000 years ago.

Tor

An isolated rocky outcrop on a moorland summit, typically formed in granite landscapes. Tors develop when freeze-thaw weathering exploits joints and weaknesses in the rock over thousands of years, leaving the hardest, most joint-free blocks standing above the eroded surface. Classic examples on Dartmoor include Hay Tor and Great Mis Tor.

Corrie (cirque)

An armchair-shaped hollow on a mountainside, formed by a glacier eroding into the slope through rotational sliding. The back wall is steep, the floor is overdeepened, and many corries contain small lakes (tarns) after the glacier melted.

Fetch

The distance of open water over which wind blows to generate waves. A long fetch produces larger, more energetic waves. The Holderness coast faces the full fetch of the North Sea from Scandinavia, contributing to high wave energy and rapid erosion.

Longshore drift

The process by which sediment is transported along the coast in a zigzag pattern. Waves approach the shore at an angle (driven by the prevailing wind), swash (rushing up the beach) moves sediment up the beach in the direction of wave approach, and backwash (flowing back down the beach) moves it straight back under gravity. The net result is sediment movement along the coast in the direction of the dominant wave approach.