Glaciers and Glacial Processes
Define ablation. What causes it?
Ablation is the loss of ice through melting of glaciers. it is cause by a rise in temperature during the summer season.
Explain glacial advance and retreat. What happens to the zones of accumulation/ablation during these glacial movements? What happens to the movement of the ice during these glacial movements?
Advance: when the amount of accumulation is greater than the amount of ablation, the upper end of the glacier gains mass and causes the entire mass to move downhill faster than before. Retreat: when ablation exceeds accumulation and the glacier begins to move downhill more slowly, allowing for the ice to melt and runoff.
Explain the ways we know about climate change on intermediate and long timescales.
Anecdotal evidence - written records - dendrochronology (tree ring dating) - isotopic ratios of O^18 & O^16 can tell us about the sea surface temperatures (SST) higher O^18/O^16 = higher SSTs, higher O^16/O^18 = lower SST
Explain the difference between a valley and continental glaciers. Give an example of both.
Continental glaciers - consist of thick, vast ice (along the poles) Ex. Antarctica and Greenland Valley glaciers - found in high altitudes, and it snows year round until it accumulates and flows down through valleys (can be found anywhere) Ex. Yosemite Valley
Explain the changes to the earth's biomes, climate, and oceans that occur during ice ages? What is loess and what does it have to do with katabatic winds?
During the ice ages, the Earth experience its coldest climate in 65 million years.
Explain what differentiates a glacial valley from one formed by fluvial processes.
Fluvial valleys usually form into a V-shape, whereas glacial valleys form U-shapes.
How does glacial ice differ from snow? What is the process that converted snow to glacier ice called?
Glacial ice is compacted snow. After years of compression and pressure the snow becomes firn. With more compression, firn becomes fine-grained ice, and eventually coarse-grained ice (due to the formation of gas bubbles between ice grains) that is essentially glacial ice. There is no name for the process.
What kind of deformation occurs in a glacier? Explain the analogy between glaciers and the lithosphere/asthenosphere.
Glaciers and the lithosphere/asthenosphere can be described as flowing plastic because although it is in solid form, it can flow/deform like melted plastic. Creep - internal deformation of ice crystals slip over one another. Sliding - movement of the entire glacier over the rock below.
How does isostasy relate to glaciation? What is isostatic rebound?
Glaciers push down on the asthenosphere, creating a depression in the lithosphere where asthenic material beneath it flows out. Either sides of the depression are called beaches. Once the glacier melts, the lithosphere rebounds because the asthenosphere can flow back to the region.
What is a moraine? Where to they form? Are the well sorted or not, why? How do they form?
Moraine - ridge of debris deposited at the margin of a glacier. Forms as sediment is carried by flowing ice to the glacier margin, where it is melted out and accumulates over time. They form as a result of the advance and retreat of glaciers.
What causes Ice Ages?
Tectonics: movement of continents to higher latitudes Global Atmosphere: CO2 levels changes caused by volcanic activity and weathering Insolation: Milankovich Cycles (eccentricity, tilt, and wobble) Feedback: albedo, deep ocean water formation, biological processes that form CO2
Explain the formation and flow of continental and valley glaciers
Valley glaciers flow downhill, continental glaciers have no obvious flow but spread.
