Large Space, Long Time

IMG_20180411_191013.jpgThe view west across Salt Lake City pulls my mind outward across both space and time. The sweeping miles of space are immediately obvious. This place is not called “viewpoint” for no reason. The eons of time are only slightly less obvious for a student of the rocks. The mountains here (in the region called the basin and range) are the upper edges of chunks of Earth’s crust that have tilted, raising one edge, dropping the other. The valleys are thousands–sometimes tens of thousands–of feet of sediment sluiced of the mountains as they rose. 20,000 years ago this place was so wet the entire flat land visible in the photo was under water–Lake Bonneville. That much rain ate at the mountains, biting their tops off as they rose. I see this same mountain-eating process in the wet mountains east of my house near Mt. Rainier. But even deluges take some time to eat mountains. Chewing 10K or 20K feet off a rising mountain takes some time. And lifting the edge of a piece of Earth’s crust 30K feet also takes some time. So, looking across the Salt Lake valley is looking across the time it took to lift the rocks in these mountains from their original flat to their present verticality. And there is more. The mountain Gus is standing on is made of limestone (at least the part right under his feet.) That limestone was created by accumulating lime sediment in a sea that used to exist here. After it accumulated, it needed time to turn to stone. And this accumulation and lithification had to happen before the crust on this region could be broken into pieces and tipped to form mountains that could be eroded to fill the valley before becoming a lake before drying out and turning the top of the valley into salt flats.

All this is on display from the Pipeline Trail Viewpoint above Mill Creek Canyon.

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