Ribbon lakes A ribbon lake is a long, narrow lake on the floor of a U-shaped valley.
Formation: • As a glacier passes through the valley, it erodes patches of softer rock from the valley floor. This leaves behind hollows.
• After the ice age, the hollows fill with water to form lakes called ribbon lakes.
• When a number of ribbon lakes are joined together by a river they are called paternoster lakes. They are called this because they resemble rosary beads.
Example of a ribbon lake: Glendalough in Co. Wicklow.
Example of paternoster lakes: The Gap of Dunloe in Co. Kerry.
(i) Can you explain why ribbon lakes got their name?
(ii) Look up photographs of paternoster lakes and rosary beads online. Do you think they look similar? Work in pairs.
Hanging valleys
A hanging valley is a smaller glaciated valley that hangs above the main glaciated valley.
Formation: • Hanging valleys contained smaller glaciers. Smaller glaciers are not able to erode as deeply as larger glaciers. This means that hanging valleys are not as deep as the main valleys.
• When the glacier melts, the floor of the hanging valley is left high above the main valley.
• A stream drops from the high hanging valley to the low main valley as a waterfall.
Example of a hanging valley: The Poulanass Waterfall in Glendalough, Co. Wicklow drops from a hanging valley.
Fjords
A fjord is a drowned U-shaped valley that is very deep and has steep sides. Formation:
When an ice age ended, the glaciers melted and the sea level rose. Glaciated valleys located near the coast were drowned and became fjords.
Example of a fjord: Killary Harbour on the border between Co. Mayo and Co. Galway is Ireland’s only fjord.
182 : Figure 11.11 Killary Harbour, Co. Mayo : Figure 11.10 A hanging valley : Figure 11.9 Ribbon lake at Glendalough, Co. Wicklow ACT VITY
