September 18, 2009

From Twin Falls to the Great Salt Lake

Then it was onto Twin Falls and the spectacular 200 foot cliffs of Shoshone Falls in the Snake River Canyon. This is the end of the historic salmon migration, as they could not possibly ascend those falls. In fact, those falls create a biogeographic separation between Pacific oriented fish species such as salmon, rainbow trout, sturgeon, and others and those with Rocky Mountain/Great Basin affinities such as Bonneville cutthroat trout. Only whe n flood waters created temporary lakes in the canyon were fish able to pass this barrier.

After a night at the nice little county campground of Rock Creek Park, we headed south into Northern Utah to Golden Spike National Historic Site, where the Union Pacific and Southern Pacific railways finally met from east and west. They had two circa 1960’s replica steam engines on display and did demonstration runs with them. Hilina was in heaven, as they went by and she waived her little Thomas the Tank Engine toy at the conductor.

That night we camped at Antelope Island State Park in the middle of the Great Salt Lake, the last remnant of the ancient Lake Bonneville that once covered over half of Utah. It is a beautiful grassland full of proghorns, bison, and coyotes yelping at dusk. We had pronghorns running right by the campsite.

We went for a quick swim in the warm Great Salt Lake, which due to its extreme salinity that is some 4-8 times saltier than the ocean, makes you extremely bouyant. I also discovered that the flat oolitic rocks on the shore are some of the most amazing skipping rocks I have ever seen. The extra heavy salt waters, in combination with the light, flat rocks, makes for rocks that seem to float across the surface until all momentum is lost.

So, what is oolitic rock? It is sand that has been glued together with calcium carbonate, sodium chloride, and brine shrimp excrement into layer rocks. They are fairly soft and pretty easily to break apart. You can tell they will become (or already are) layers of sedimentary rock that future geologists will study.

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