ponds and lakes
Ponds are small bodies of fresh water that usually have no outlet; ponds are often are fed by underground springs. Like lakes, ponds are bordered by hills or low rises so the water is blocked from flowing directly downhill.
Lakes are larger bodies of water. Lakes are usually fresh water, although the Great Salt Lake in Utah is just one exception. Water usually drains out of a lake through a river or a stream and all lakes lose water to evaporation. Lakes form in a variety of different ways: in depressions carved by glaciers, in calderas (Figure 1.1), and along tectonic faults, to name a few. Subglacial lakes are even found below a frozen ice cap. As a result of geologic history and the arrangement of land masses, most lakes are in the Northern Hemisphere. In fact, more than 60% of all the worlds lakes are in Canada most of these lakes were formed by the glaciers that covered most of Canada in the last Ice Age (Figure 1.2). Lakes are not permanent features of a landscape. Some come and go with the seasons, as water levels rise and fall. Over a longer time, lakes disappear when they fill with sediments, if the springs or streams that fill them diminish, (a) Crater Lake in Oregon is in a volcanic caldera. Lakes can also form in volcanic craters and impact craters. (b) The Great Lakes fill depressions eroded as glaciers scraped rock out from the landscape. (c) Lake Baikal, ice coated in winter in this image, formed as water filled up a tectonic faults. Lakes near Yellowknife were carved by glaciers during the last Ice Age. or if their outlets grow because of erosion. When the climate of an area changes, lakes can either expand or shrink (Figure 1.3). Lakes may disappear if precipitation significantly diminishes. Large lakes have tidal systems and currents, and can even affect weather patterns. The Great Lakes in the United States contain 22% of the worlds fresh surface water (Figure 1.1). The largest them, Lake Superior, has a tide that rises and falls several centimeters each day. The Great Lakes are large enough to alter the weather system in Northeastern United States by the lake effect, which is an increase in snow downwind of the relatively warm lakes. The Great Lakes are home to countless species of fish and wildlife. Many lakes are not natural, but are human-made. People dam a stream in a suitable spot and then let the water back up behind it, creating a lake. These lakes are called "reservoirs." Click image to the left or use the URL below. URL:
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a small body of fresh water with no stream draining it.
a) lakes --> b) ponds c) ocean d) stream
which of these is not full of fresh water?
a) the great lakes b) glaciers --> c) the great salt lake d) ponds
the water in crater lake in oregon is within a(n)
--> a) caldera in a volcano. b) fault zone. c) glacially carved basin. d) impact crater.
the great lake basins were made from
a) calderas in a supervolcano. b) erosion due to giant floods. c) a set of meteorite impact craters. --> d) glacially carved rocks.
every lake you see was formed naturally.
a) true --> b) false
lakes formed in canada were from glaciers that covered north america in the last ice age.
--> a) true b) false
lakes change with time, including
a) rising and falling with the season. b) filling with sediment. c) getting deeper with erosion. --> d) all of these.
lakes are not like the ocean because they are made of fresh water and they do not have tides or currents.
a) true --> b) false
a) have living organisms at the surface but are too deep for life to live at the bottom. b) only form in fault zones where blocks of crust drop down to form a basin. --> c) alter weather by increasing snow downwind. d) all of these.
the great salt lake is salty because
a) fresh water drains out of the lake and leaves salt behind. --> b) fresh water evaporates and leaves salt behind. c) the lake formed on a halite formation and that salt has since dissolved into the lake. d) none of these.
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