Geography · Ch 12 — Landforms and their Evolution
High Rocky Coasts
High Rocky Coasts
High rocky coasts begin with a striking visual: rivers appear drowned, and the coastline is highly irregular and deeply indented. Where glacial valleys meet the sea, water pushes far inland, forming fjords. The hillsides drop off sharply into the water, and the shore initially shows no depositional landforms at all — erosion dominates completely.
The waves break with great force against the land, hammering the hillsides into cliffs. With constant pounding, these cliffs slowly recede, leaving behind a wave-cut platform in front of the sea cliff. Over time, the waves gradually smooth out the irregularities along the shore. The material that falls off the sea cliffs and gets carried away breaks into smaller fragments, rolls to roundness, and eventually gets deposited offshore.
After a considerable period of cliff development and retreat, the coastline turns somewhat smooth. As more material is added to the offshore deposit, a wave-built terrace develops in front of the wave-cut terrace. Meanwhile, the ongoing erosion supplies plenty of material to longshore currents and waves, which deposit it as beaches along the shore and as bars in the nearshore zone.
- Bars — long ridges of sand and/or shingle lying parallel to the coast; they are submerged features.
- Barrier bars — bars that show up above the water surface.
- Spits — barrier bars that get keyed up to the headland of a bay.
- Lagoons — formed when barrier bars and spits block the mouth of a bay. …
Along high rocky coasts, rivers appear to have been drowned, with a highly irregular, indented coastline where glacial valleys (fjords) are present -- hill sides drop off sharply into the water. Shores do not show any depositional landforms initially; erosion features dominate. Waves break with great force against the land, shaping the hill sides into cliffs; with constant pounding, the cliffs recede leaving a wave-cut platform in front of the sea cliff, and waves gradually minimise the irregularities along the shore. Material that falls off and is removed from the sea cliffs gradually breaks into smaller, rounded fragments and gets deposited offshore. After a considerable period of cliff development and retreat, when the coastline turns somewhat smooth, a wave-built terrace develops in front of the wave-cut terrace. As erosion along the coast supplies material to longshore currents and waves, they deposit it as beaches along the shore and as bars (long ridges of sand and/or shingle parallel to the coast) in the nearshore zone. Bars are submerged features; when exposed above water they are called barrier bars. A barrier bar keyed up to the headl …