glaciated landscapes 3 Flashcards
erosional and depositional feaures of lake district case study
Corrie: Red tarn, 720m, area of 0.46 km2, orientatednorth east, back wall is 216m.
Arete: striding edge, length of 1km
Hanging valley: GLenridding beck, length of 5km
Glacial trough: Patterdaale, 13km, valley sides are 200-300m, width of 2km
Ribbon lake: Ullswater, 11km long, width of 900m
rouche moutonne: Norfolk island: area 1000m2
HUmmocky morraine: Glenridding beck
End morraine: Lip of red tarn
Drumlins: Eden vale, 308 drumlins, 36km2 area
Erratic: near allonby, were transportd from a glacier 25 km away.
physicla factors influencing the formaion of landforms
1 - altitude: LD is upland area, highest mountain in england:978m scaffel pike. Cool temmps at colder altitudes (mean temp of 8c). More FTW in higher altitudes as its cold enought to freeze, more erosional landforms, more diagenesis, corrie glaciers.
2 - Geology: Skiddaw: north, rounded mountains, slate. Borrowdale volcanic group: crystalised rock with lots of joints, resistant to ftw,igneous rock, jagged and angular. Winde,ere: soft, least resistant to erosion, sedimentary. Borrowdale volcanicss has more FTW and more landforms also highest mountains, rugged topography.
3 - climate: HIgh altitude = colder and wetter climate, cold climate led to corries forming due to high altitude and cold climate. High altitde = more recipitation in the form of snofall so more accumulation and glacier formation.
4 - Aspect: Corries mainly face north or north east, they don’t face the sun: north east is cooler so more accumulation and diagenesis and glacier foorms and moves creating erosional landform.
interconnectedness of landforms in the lake district
- eastern side og Helvellyn was the source for glaciers whose corries e.g. red tarn can be seen. Wherethe glacier formd there is anarrow ridge of land seperating 2 corries: striding edge. There are no corries on the west side of Helvellyn so no pyramidal peak.
- Glacier moves downhill, flows over corrie lip following the line of a river valley. The glacier flows down the hanging valley of glen ridding beck down to the village below.
- Here it joined a larger glacier in the valley of Patterdake, the small tributory glacier from red tarn has erosive power, glen ridding back was changed from a river valley to a deep glacial trough. As the glacier moved to the north it replaced the v-shaped valley to a u-shaped valley, eroding spurs making them truncated.
- Glacial troughs are not smooth. After oce retreated the rock basin filled with meltwater an rain: rbbon lake: Ullswater. In Ullswater here is some raised igenous sill, the glacier slid over it forminga roche moutonee: norfolk island.
- WHen glacier melted and retreated, depositional features created: drumlins and erratics and morraine.
introduction to the laurentide ice sheet
- Ice ages are large accumulations of ice extending >50,00km2. Ice sheets possess 69% of the world’s ice. During the lsat ice age (Pleistocene), other ice sheets existed such as laurentide ice sheet in north america.
- it was centred in Hudson Bay and covered NA miltiple times during the quaternary period (2m years a go). In a colder period it extended down to Minnesota. The last of the glacial periods in NA was the Wisconsin ice age: 95,000 to 12,000 yrs a go. It was at its maximum extent 21,000 years a go but then retreated. At its aximum extent it covered 13,000,000sqkm, reaching as far south as 37N. Reached thicknesses of 2-3km.
erosional landforms created by the laurentide
1 - erosional impact on mountains: The ice sheet wore down many mountains, highest peaks are now 500-700m. But erosional features are deeper due to the thickness of the ice sheet = more pressure = more erosion.
2 - ellipsodial basins: Huge lake basins created by erosion, Hudson bay is the largest basin formed (1,230,000km2). Laurentide ice sheet was centered in what is now Hudson bay, the ice sheet was ellipsodial in shape: thickest at its centre(more erosion and pressure here).
3 - great lakes: Make up the world’s largest lake system and are lesser ellipsodial basins. 5 lakes: Lake superior, Lake Huron, Lake ontario, Lake michigan, Lake erie. Great lakes occupy former river valleys that were enlargened and deepend by glacial erosion via ice lobes(togue shaped glaciers exending from the margins od the main LIS)WHen it advanced, soft rock was eroded ice lobes advanced and retreated: forming ellipsodial asins. When retreated, meltwater filled basins.
depositional landforms created by lis
1 - till sheets and morraine: till was deposited across minnesota. Wadena lobe advanced from the north - till that was red and sandy from red sandstone to the north & east. Raint and superior lobes: north east and advanced, left till of basalts, granite in minnesota. Des Moines lobe: originated from north west and advanced south east, deposited till of limestoe and shale, some till deposits over 160m in depth.
2 - drumlins: large drumlin fields across new york. NY contains one of largest drumlin fields: 12,000km2consists of 10,000 drumlins. In a lowland area so ice spread out,lost mass and energy and deposited material bu ice still flowed and created drumlin shape.
3 - erratics: South west minnesota: three maidens rocks came as one huge boulder (15m diametre), split into six pieces. The granite boulders contrast with quartize bedrock nerest granite is 90 miles.
