Topographic Maps

Topographic maps are mostly regarded as back country road maps, good for knowing where you are. Their use can be more extensive providing details about locations to prepare you for the landscape that you will encounter. Unlike other maps, topographic maps try to give a complete picture of their piece of earth, a kind of photographic record of the landscape.

Topos use more than 150 symbols to distinguish things from Glaciers to swamps. Most important are the brown contour lines representing the land itself its mountains and valleys, ridges and canyons, plains and plateaus. Topographic maps will vary in scale, contour interval, age, and the amount of territory covered (Brownridge).

When contour lines cross a stream they bend upstream in a V and flow is then in the opposite direction. Contour lines also help specify a regions depth; steep slopes are shown by closely spaced contours, gentle slopes are characterized by widely space contours. Contour lines are one of many ingredients for topographic maps. Spot elevation lines also play a very important role in deciphering heights of some point of interest such as a house, hilltop, lake level, etc. (Johnston, et.al.).


Glaciers

Glacier Photo from Winona Museum, taken from:

A glacier is a massive, long-lasting accumulation of compacted snow and ice that forms on land. About ten percent of the earth's land is covered by glaciers and they hold 75% of our fresh water. There are two types of glaciers: alpine, which is restricted to mountain ranges; and continental, which covers large parts of continents. Because of the glaciers weight and gradual movement, erosional and depositional features change the landscape over hundreds or even thousands of years.

Alpine glaciers erode bedrock creating various landforms, such as: cirques, steep-sided depressions eroded into peaks; aretes, thin, sharp, ridges separating two glacial valleys; horns, pyramid-shaped peaks formed by the intersection of three or more cirques (Thompson & Turk).

Sediment is also transported and deposited by glaciers and the terrain is blanketed with till or unsorted material that forms large mounds called moraines. There are several different moraines; terminal, ground, recessional, lateral and medial and drumlin that are a result of the abrasion by glaciers.

Works Cited

Brownridge, Dennis ; “Back Country Blueprints: Topographic Maps Put the Lay of the Land Right in Your Hands.” Backpacker 13 (1985) : 72(3).

Thompson, Graham R. and Jonathan Turk. Earth Science and the Environment. Saunders College Publishing: Fort Worth; 1992.

Johnnston, Paul, Aber, Susan and Ye, Hengchun. Introduction to Earth Science Lab. Burgess Publishing: Edina; 1996.

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