glaciation

ccc geography 2nd year

define climate

weather conditions in an area measured over 30 years

different methods of erosion by glacier

plucking

abrasion

plucking

as ice moves it causes friction between the ice and the ground, friction creates heat which causes the base of the ice to melt. this meltwater flows into the cracks in the rocks which then refreezes around the rock when the glacier moves again it pulls or plucks chunks of the rock from the ground

abrasion

plucked rocks become embedded in the glacier and as it moves the rocks abrade the surface over which they pass

features of glacial erosion

glaciated valley

cirque

tarn

pyramidal peak

arete

paternoster lakes

truncated spur

hanging valley

fjords

glaciated valley

this is a V-shaped valley which has been straightened and flattened by the movement of a large glacier to become a U-shaped valley

formation:

1. during an ice age a glacier fills the valley

2. plucking occurs enlarging the valley

3. abrasion occurs enlarging the valley

4. the valley has become U-shaped

examples:

Glendalough, Co. Wicklow

Doolough valley, Co. Mayo

cirque

also known as a corrie this is a large hollow on the side of a mountain. it has three steep sides and is the birthplace of a glacier

formation:

1. snow collects in a mountain hollow over time the snow compacts to form a glacier

2. through abrasion, plucking and freeze thaw action the hollow grows deeper

3. when a glacier is big enough it starts to flow over the edge of the cirque

4. when the glacier ice melts a lake called a tarn may be left in the cirque

5. when two cirques form back to back the ridge between them is known as an arete

examples:

devils punch bowl, Co. Kerry

coumshingaun logh in the Comeragh mountains Co. Waterford

tarn

this is a lake inside a cirque

pyramidal peak

this is a steep sided pyramid shaped mountain that was eroded on all sides by many cirques

arete

this is a narrow steep sided ridge between two cirques

paternoster lakes

when a long narrow lake occupies the floor of a glaciated valley it is called a ribbon lake when a few ribbon lakes meet it is called a paternoster lake

truncated spur

this was originally an interlocking spur that was eroded having its head cut off as the glacier moved through the valley

hanging valley

this is a small tributary valley that hangs above the main glaciated valley

fjords

a fjord is a U-shaped valley found under the sea

they were formed when the glacier retreated after carving out a U-shaped valley. as the sea level rose the U shaped valley ended up under water

example:

killary harbour Co. Mayo

glacial transport

supraglacial

englacial

subglacial

supraglacial

materials found on the surface, top or sides of glaciers

moved along when a glacier moves

usally has fallen from mountains

englacial

any regolith trapped within the ice

subglacial

loose regolith trapped underneath the glacier

features of glacial deposition and transportation

terminal moraine

drumlin

erratic

esker

outwash plain

moraine

mass of rocks and other materials carried down by the glacier

types:

recessional - marking a temporary stop or retreat of glacier

terminal - front of glacier, material pushed ahead of glacier, end point of glacier

lateral - side of glacier, broken rock and soil form supraglacial material

medial - middle when two glaciers combine, two lateral moraines combine

drumlin

oval shaped hills that are made of deposited boulder clay.

formation:

1. glacial ice depsoites boulder clay in irregualr heaps

2. the ice retreats and advances again this time it shapes and smooths the boulder clay into rounded oval-shaped hills

3. the steep slope of the drumlin is the direction from which the ice advanced . the gentle slope points to the direction in which the ice was travelling

examples:

clew bay, Co. Mayo

lower lough erne Co. Fermagh

erratic

larger boulders that were deposited by ice in an area where the rock type of the area is quite different to the rock type of the boulders

example:

the Burren, Co. Clare

esker

long winding ridge of sand or gravel

formation:

1. as the ice melts large tunnels of meltwater flow in tunnels beneath the oce

2. when a river leaves an ice tunnel it slows down immediately and deposits material at the mouth of the tunnel

3. as the ice slowly melts bakc the deposited material is dropped in the form of a long narrow ridge of sand and gravel

example:

trim esker system, Co. Meath

outwash plain

a flat area of sand and gravel found in front of a terminal moraine

formation:

1. as the sheet melts huge amounts of meltwater flow out of it

2. the water flushes large quantities of sand and gravel onto the lowland beyond the front of the ice

example:

the curragh, Co. Clare