Glaciated Landscapes SG5 Flashcards
What is Lake Palcacocha?
A proglacial lake which has formed at the snout of the Palcaraju Glacier
What altitude is Lake Palcacocha at?
4,566m A.S.L
What valley does the Rio Grande flow down to get to Huaraz?
Cojup Valley
How long is the Cojup Valley?
20km
How did Lake Palcacocha form?
A body of water forms between the snout of a glacier and the end moraine from meltwater and rainfall. As the glacier retreats more water is trapped in the lake.
What is the altitude of Huaraz?
3,058m A.S.L
What is the mean temperature of Huaraz?
13.5 degrees C
What is the Environmental Lapse Rate?
Temperature decreases by 6.5 degrees C for every 1km
What is the mean temperature at Lake Palcacocha?
3.7 degrees C
What is the rate of precipitation in winter in Huaraz?
130mm/month (most will fall as snow)
What is the rate of precipitation in summer in Huaraz?
5mm/month
What are three management strategies of the Peruvian Government for Lake Palcacocha as climate warms?
An 8m dam to help reinforce the terminal moraine, Artificial lowering of the lake by 3m since 2010, Glacial Lake Management Team controls the volume of water in the lake with pipes which drain excess meltwater
When was the 8m dam completed?
1974
What does the dam include?
A concrete overflow spillway which controls the water level in the lake
What did the artificial lowering of the lake involve?
Siphoning off water from the lake through drainage pipes
What is the aim of the Glacial Lake Management Team?
Prevent the mean depth of the lake exceeding 30m
What is the mean temperature increase of the Peruvian Andes since the 1940s?
Between 3 and 5 degrees C
What is the % increase in the area of the lake in m squared between 1972 and 2009?
676%
What is the % increase in the volume of the lake in m cubed between 1972 and 2009?
2,890%
What is the % change in the potential energy of the lake between 1972 and 2009?
10,858%
How many GLOFs have there been in the past?
Three - 1941, 2003, 2007
What is the impact of the increase in potential energy stored in Lake Palcacocha on a potential GLOF?
More potential energy means that if the lake topples over the moraine dam, the water would have more kinetic energy so would travel faster down the Cojup Valley
What was the cause of the 1941 GLOF?
Huge chunk of the glacier fell into the lake, created a huge wave from the displacement of water which overtopped the end moraine creating a GLOF down Cojup Valley
What are three impacts of the 1941 GLOF?
Blocks of ice, boulders and mud carried toward the Santa River Valley, 400m3 of debris buried parts of Huaraz, Killed 6,000-7,000 people
What are two causes of the 2003 GLOF?
Part of the steep lateral moraine slid into the lake, Heavy rainfall over-saturated the moraine material
How big was the wave which created the 2003 GLOF?
8m
How big was the wave which created the 2007 GLOF?
3m
What damage did the 2007 GLOF cause?
Damaged all 10 of the pipes used to control the lake height
What is the % decrease in the potential energy of the lake after the 3m artificial lowering of the lake?
47%
How has the Glacial Lake Management Team impacted flows of material?
The lack of flow in the lake means a lack of energy and the deposition of sediment onto the lake bed (sedimentation)
Why is the water flowing down the Cojup Valley clear?
The trapping of sediment in the lake means that only clear water containing very fine rock flour is transported in the stream below the dam
Why might sedimentation into the lake be of concern to the Glacial Lake Management Team?
It would decrease the capacity of the lake to store water which increases the risk of another GLOF
