Lithosphere

Physical environments

Corrie

A steep-sided, armchair-shaped hollow with a rock lip, formed by glacial erosion. Snow collects in a hollow, compacts into ice, and moves in a rotational motion due to gravity, eroding the back wall and deepening the hollow by plucking and abrasion.

Arête

A narrow ridge formed when two corries develop back-to-back or side-by-side, eroding towards each other. Plucking and freeze-thaw weathering sharpen the ridge between them.

Pyramidal peak

A sharply pointed mountain peak formed when three or more corries erode back into the same mountain. The surrounding corries and arêtes leave a horn-shaped summit.

U-shaped valley

A steep-sided, flat-bottomed valley formed by glacial erosion. A glacier widens and deepens a V-shaped river valley through plucking and abrasion, creating a U-shaped cross-section.

Hanging valley

A smaller tributary valley that joins a main U-shaped valley from a higher elevation. The main glacier erodes more deeply than the smaller tributary glacier, leaving the tributary valley 'hanging' above the main valley, often with a waterfall.

Ribbon lake

A long, narrow lake in a glacial trough, formed when a glacier erodes softer rock more deeply than surrounding hard rock. When the glacier melts, water fills the over-deepened section.

Drumlin

A smooth, elongated hill of glacial till (unsorted material) deposited beneath a glacier. Shaped like an inverted spoon, with the blunt end facing up-valley and the tapered end pointing down-valley, indicating the direction of ice flow.

Esker

A long, winding ridge of sorted sands and gravels deposited by meltwater streams flowing in tunnels beneath a glacier. Formed as the glacier retreats and deposits material.

Terminal moraine

A ridge of unsorted material (boulders, clay, sand) deposited at the furthest point reached by a glacier. It marks the maximum advance of the glacier and forms a mound across the valley floor.

Wave-cut platform

A flat area at the base of a cliff formed when erosion (mainly abrasion and hydraulic action) cuts into the cliff, causing it to collapse. Over time, repeated collapse and retreat leave a gently sloping rock platform exposed at low tide.

Headland and bay

Formed on discordant coastlines where bands of hard and soft rock run perpendicular to the coast. The soft rock is eroded more quickly, forming bays, while the hard rock resists erosion, forming protruding headlands.

Cave

A hollow in a cliff formed by erosion of weak points (joints or faults) by hydraulic action and abrasion. Continued erosion enlarges the opening into a cave.

Arch

Formed when a cave on either side of a headland erodes through to meet in the middle, creating a natural archway. Weathering and erosion continue to weaken it over time.

Stack

A tall, isolated pillar of rock left behind when the roof of an arch collapses due to weathering and gravity, separating it from the headland.

Spit

A long, narrow ridge of sand or shingle projecting from the land into the sea, formed by longshore drift. Material is deposited where the coastline changes direction. The end may curve due to changing wind and wave directions.

Bar

A spit that grows across a bay, joining two headlands. It traps water behind it, forming a lagoon. Formed where there is no strong river current to prevent deposition across the bay.

Tombolo

A spit or bar that connects the mainland to an offshore island. Formed by longshore drift depositing material between the two landmasses.