glaciated landscapes 5

Question 1

introduction and formation

Answer 1

-Lake palcacocha is a proglacial lake >4000m, formed at snout of the palcaroju glacier in the Andes, Peru, formed when retreating glacier’s meltwater was damned by moraine.
- river from palcacocha combines with other tributaries to flow down cojup valley to city Huaraz 20km down below.
- Formed: As glacier retreats, side and end moraine build up acting as boundaries, meltwater fills it up.
- mean temp is 3.7 C, precipitation in winter.

Question 2

glacial lake management

Answer 2

• An 8 metre dam was completed in 1974 to reinforce terminal moraine - a concrete overflow spill way to control water.
• since 2010, the lake has had to be artificially lowered by 3 metres via siphoning off water through drainage pipes, aim is to prevent mean depth exceeding 30 metres.
• Why manage the lake? Peruvian Andes has had a mean temp increase of 3 degrees since 1940s. The volume of the lake has increased by 3000% and an area by 700% and a 10,000 increase in potential energy.

Question 3

hazards created by the lake

Answer 3

• increase in potential energy: increases rick of glacial lake outburst flood - 3 in the past.
• huge potential energy convert to kinetic, its huge mass may flow over moraine, convert to kinetic and move downstream quickly.
• 1941: huge GLOF event - huge chunk of ice fell into lake creating wave, overtopped moraine. Water carried ice, rock, mud and within 15 min the mudslide reached Huaraz. 400m3 debris buried town, 6000-7000 killed.

Question 4

effect on changing glacial landforms

Answer 4

• glacial lake management team control volume of water in lake, use pipes to drain excess.
• during dry season when it exceeds depth, water is siphoned from lake which feeds into Rio partia downstream of the dam
• increase runoff into river prevent it drying up. Excess energy of stream = more channel erosion = wider and deeper.
• maintained water level = less size fluctuation = marginally effected landscape.