Souvenirs of the Ice Ages EarthCache
Souvenirs of the Ice Ages
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An earthcache at a Rest stop on Highway 200.
"An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers." (Wiki)
Highway 200 near here passes through one of the most spectacular ice-age landscapes in Montana. Glaciers advanced out of the Mission and Swan ranges, and the mountains in the Bob Marshall-Scapegoat wildernesses, forming an ice cap that nearly filled in the valleys to the peaks from Salmon Lake to the Flathead Valley, about eighty miles north of here. Glaciers sculpted all the rugged mountain peaks of the mountain ranges you can see from the rest area. This ice cap at one time was connected to the vast Cordilleran Ice Sheet that extended into the United States from the Canadian Rockies.
Glaciers formed in this area multiple times over about the last 300,000 years. The two most recent ice ages were the Bull Lake and Pinedale. The Bull Lake glaciation began about 200,000 years ago and ended about 130,000 years ago. About 140,000 years ago, the glaciers flowed farther south of this point into the valleys south of Ovando and Helmville. Between 60,000 and 15,000 years ago the ice cap formed again. Southward spreading glaciers carried gravel and sand into the Ovando area, about one to two miles south of Highway 200. Melting glaciers left behind mounds of rock and soil debris, called moraines. The low areas between the moraines mark places where the glacial till wasn’t deposited, leaving hollows that filled with water. Many of the ancient hollows can still be seen today as wetlands, shallow ponds and small lakes. Large depressions north of here along Highway 83 are called kettles. Masses of ice buried in the outwash gravels melted forming the depressions.
The smooth broad plains to the north and east of here are glacial outwash plains. They were once the location of raging streams that carried meltwater loaded with mud, sand, gravel from the front of melting glaciers. These valleys are now the agricultural land along the Clearwater and Blackfoot rivers.
Optional Geo-Activity:
Glaciers carry rocks in from areas that can be faraway from Montana. The rocks form deposits of everything from rounded gravel to huge boulders. Look for big boulders that look out of place next to the highway. They will have a variety of different colors, banding, and textures indicating different types of bedrock.
To log this cache send an email to the cache owner with the following answers.
1. Name two types of moraines you are likely to be able to identify in a heavily glaciated area like this. (see signboard illustration)
2. North America has experienced as many as twenty ice ages but scientists only know a great deal about how many of them?
3.The causes of ice ages are not fully understood for both the large-scale ice age periods and the smaller ebb and flow of glacial–interglacial periods within an ice age. While scientists don't know everything about the causes of ice ages, name one theory explained at this location that is considered a likely cause of glacial-to-non glacial cycles?
4.What geographic portion of Montana was covered by the Cordilleran Ice Sheet?
Go ahead and log your find after sending your email to cache owner. Thanks for stopping at this cache. I hope it was educational and maybe even fun!
CACHE OWNER WILL ONLY RESPOND TO INCORRECT/INCOMPLETE EMAILS
Resources: Signage at the coordinates
Wikipedia - "Ice Ages" "Bull Lake Ice Age"
About.com - Glacier Deposition and Moraines
Additional Hints
(No hints available.)