Glaciers Rivers of Ice
Glacier Facts • Found on every continent- even Africa! • Cover 10% of the earth’s land area • Contain 75% of the freshwater on earth • Two types: • Alpine (valley glaciers) are found in the mountains • Continental glaciers (ice sheets) are found at the north and south poles
How does a glacier form? • Form when more snow falls than melts in one year • Snow compacts into ice • Ice begins to flow downhill under its own weight
How do glaciers work? • In winter, ice accumulates at the top of the glacier, pushing the glacier downhill • In summer, ice melts at the bottom of the glacier • If the amount that melts in the summer is more than the amount that accumulates in the winter, the glacier retreats
Retreating Glaciers and Global Warming Holgate Glacier, Alaska, July 1909 Holgate Glacier, August 2004
Retreating Glaciers and Global Warming Qori Kalis Glacier, Peru, July 1978 Qori Kalis Glacier, July 2004
How are glaciers affected by global warming? • All glaciers are getting smaller every year!! • Sea level is rising…coastal cities could flood!
Why do geologists care about glaciers? • Glaciers have shaped the landscape that we see now!
Glacial Landscapes Yosemite Valley, Yosemite National Park, CA Glacier National Park, Montana The Matterhorn, Switzerland- Italy Border
Glacial Erosion • As a glacier moves down the side of the mountain, it scrapes off pieces of the surrounding rock • Over time, a large amount of material can be removed by the glacier
Glacial Features: U-Shaped Valleys • When a river erodes a valley, the valley becomes V-shaped • Glaciers are wider than rivers, so they change the shape of the valley • Valley becomes U-shaped
Glacial Features: Sharp Ridges (Aretes) • Two glaciers on two sides of a mountain • When glaciers melt, a sharp ridge remains
Glacial Features: Pyramid Peak (Horn) • A peak where several sharp ridges meet • At least 3 very steep (nearly vertical) sides • Form where several glaciers meet
Citations • Lonnie G. Thompson, Byrd Polar Research Center, the Ohio State University