Lake Lahontan is a pluvial lake that formed within the western
portion of the Great Basin, occupying the majority of northwestern
Nevada during the middle to late Pleistocene. A pluvial lake is one
that has had considerable fluctuations in water levels primarily
due to climatic changes and fluctuations in precipitation and
evaporation rates. Lake Lahontan formed at a time when regional
climatic conditions were much different than they are today.
Precipitation in the Great Basin region was at a much higher level
than it is today, and evaporation rates were very much decreased,
allowing for the formation of a large inland body of water within
the enclosed basin complex. Presently, Lake Lahontan exists only as
several small remnant lakes that have managed to survive due to
perennial tributary streams.
Lake Lahontan was the second largest pluvial lake in the
northern hemisphere, covering approximately 21,000 km² during its
period of high water level. The basin which encompassed Lake
Lahontan covers the majority of the northwestern portion of the
Great Basin, and extends between approximately 117° 30’, and 119°
30’ west longitude, and 38° 30’, and 41°30’ north latitude. The
drainage basin covers approximately 115,000 km² and extends from
the northwest corner of Nevada to the northeast portion of
California, and north into Oregon.
Lake Lahontan’s history begins approximately 12 to 15 Ma with
the final stages of the Great Basin’s formation. During this
period, the upper plates began a series of faults that were upward
steepening and that surfaced as normal faults. This period of
detachment faulting continued on into the early Pliocene (approx. 5
Ma) causing the Great Basin to expand by almost 50 percent.
It wasn’t until the Pliocene to early Pleistocene that the west
edge of the basin was completely enclosed by the Sierra Nevada
Range. Previous to this time period, water could flow out of the
Great Basin through channels in the young Sierra Nevada. During the
Pliocene and Early Pleistocene, the Sierra Nevada were tilted
westward by a series of heavy uplift. This formation created a
completely enclosed basin with very few inflows or outflows.
Pluvial lakes are, by definition, lakes that have had
considerable fluctuations in water levels primarily due to climatic
changes and fluctuations in precipitation. The Pleistocene is the
only time period known to have had enough fluctuation in climatic
patterns and precipitation levels to produce pluvial lakes of any
magnitude. Pluvial lakes are formed within closed basin formations
that have no through-drainage outlets into surrounding fluvial or
coastal systems. Because of this restriction, ancient pluvial lakes
of North America, as well as their modern day remnants, are mainly
found in the arid and semi-arid regions mostly within the Great
Basin itself.
You are standing in front of Honey Lake, one of three remnants
of Lake Lahontan.
To log this earthcache please email me the following answers:
What are the names of the other 2 remnant lakes of Lake
Lahontan?
What is the name of the Geologist who in 1885 drew a map of the
lake at its highest level?
Looking at the map at the kiosk estimate a percentage of how
much of the ancient lakes has disappeared and how much remain.
Look at Honey Lake shoreline, estimate how much of the lake is
water and how much of it is shoreline.
To prevent armchair logging, post a picture of you at the bench
at the above coordinates. Try your best to get the receding lake
into your shot. I don't need to see you gps, but I do need to at
least see your forehead or group shot.
Do not wait for me to post your find, but if I don't receive
your answers within one week of logging I will delete your log.