Download ancient lake bonneville

ANCIENT LAKE
BONNEVILLE
How deep was
Lake Bonneville?
At its largest, the
lake covered an
area of nearly
20,000 square
miles, and
reached a depth
of nearly 1,000
feet above the
current Great
Salt Lake.
Fun Fact: After
his exploring
expedition in
1833, Captain
Benjamin
Bonneville was
the first to
write about the
former
existence of
the giant lake
that had
disappeared
long before his
arrival.
Ancient Lake Bonneville
Over many years, Ice Age temperatures became warmer and the ice slowly melted. The water
formed a huge lake that spread over the flat land of the Great Basin. It covered much of Utah, spreading
through canyons and mountain valleys.
The waves of Lake Bonneville washed against the sides of the Wasatch Mountains until a flat
bench, or terrace was formed. Over the years, the size of the lake changed because the warming climate
caused the water to evaporate. Each change left a new bench mark on the side of the mountain.
Mountain streams flowed down to the lake, carrying loads of sediment. As the streams entered
the lake waters, their speed slowed down and they spread out over the land, dropping much of the rich
mountain soil and small rocks they carried. These sediments formed wide areas of loose soil, gravel, and
sand, and are now some of the best soil and gravel deposits in the state.
Finally, about 8,000 years ago, the water overflowed and broke through Red Rock pass in the
northern end of Cache Valley. It rolled to the Pacific Ocean through the Snake and Columbia Rivers. This
lowered the level of the lake to what it is today.
The major remnants of Lake Bonneville are the Great Salt Lake, Utah Lake and Sevier Lake.
Since the Great Salt Lake is what Geologists call a “sink” it doesn’t have an outlet running out of it. The
water enters the Great Salt Lake and either “sinks” into the ground or evaporates. After doing this for
thousands of years the mineral deposits keep building up so the Great Salt Lake is very rich in minerals
and salt. Utah Lake has remained a freshwater lake because it has an outlet as well as inlets. Sevier Lake
is dry most of the time since the Sevier River that feeds it is used for irrigation.
Write 5 facts about Lake Bonneville you learned from the paragraphs above.
1. ___________________________________________________________________________________
2. ___________________________________________________________________________________
3. ___________________________________________________________________________________
4. ___________________________________________________________________________________
5. ___________________________________________________________________________________
Answer the following questions in complete sentences (use the map on the back, if needed):
1. Which of Utah’s 3 regions was affected most by Lake Bonneville? Do you think there was a difference
in climate in that region when it was covered by Lake Bonneville? Why?
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After writing your 5 facts and answering the questions, turn to the map on the back and do the following:
- Label Syracuse City. Was Syracuse buried under 1,000 feet of water? In other words, is
Syracuse City in the boundaries of Lake Bonneville? ___________________________________
- Draw and label Utah Lake and Sevier Lake (look on pg. 22 of the old Utah Studies textbooks).
- Color the Great Salt Lake, Utah Lake and Sevier Lake RED.
- Color Lake Bonneville YELLOW.