Posted by Chris M Monday, November 24, 2008

Map Monday #2: Glaciers of the Alps

One of the first important research foci of early (19th century) geology was the Alps and their associated glaciers. People like De Saussure and Agassiz were climbing around the mountains (helping to invent the sport of mountaineering) trying to understand the processes involved.

This week's map is from 1854 and illustrates features of several Alpine glaciers. Not only is the speed of the glacier shown, but also the location of moraines and erratic boulders. These features were the first evidence of ice ages in the earth's past.

Just like last week's map, this is from the David Rumsey Collection.

Illustrations of the glacier systems of the Alps and of glacial phenomena in general. From the surveys and sketches of Professor Forbes, the maps of Raymond, Weiss, Charpentier &c., by A.K. Johnston, F.R.S.E. Engraved by W. & A.K. Johnston. William Blackwood & Sons, Edinburgh & London. 1st. November 1854. (1856)

Posted by Chris M Monday, November 17, 2008

Map Monday #1: Lake Bonneville

With such great post series like where on google earth, geopuzzles, and the alliterative sea-floor Sunday, Friday faults, and Friday field foto, when not start out the week with map Monday?

The map is of the pluvial Lake Bonneville, completed during the Wheeler Survey, one of the large "west of the 100th meridian" surveys that helped to establish the USGS in the 1870s. The data for the map was gathered in part by the great 19th century geomorphologist, G. K. Gilbert. The map is part of the David Rumsey Map Collection. Click on the image for a larger look. If you also have time, check out this neat little flash "brief history of Lake Bonneville" from the Utah State Geological Survey.

Restored Outline Of Lake Bonneville. Geological Data By G.K. Gilbert & E.E. Howell. J. Bien lith. Portions Of Western Utah & Eastern Nevada. Expeditions of 1869, 1871, 1872 & 1873 Under the Command of 1st. Lieut. Geo. M. Wheeler, Corps of Engineers, U.S. Army. U.S. Geographical Surveys West Of The One-Hundredth Meridian. (1876)

Posted by Chris M Sunday, November 9, 2008

Desert Lake and Dune Field

Desert lake and Sand Dune Field from Google Earth.

Last weekend I took a trip to Desert Lake located in the Desert National Wildlife Refuge. The lake is a large dry playa located in Desert Valley, an endorheic basin. An endorheic basin, also known as a closed basin, has no water exiting or leaving it. The valley itself is located on the southern side of the larger endorheic Great Basin. Because of the unique names of the playa and valley, I haven't been able to find much published literature about the area.

Desert Valley drains an area starting at the Groom and Tikaboo ranges near Rachel, through Nellis Air Force Range, before terminating at Desert Lake.

Although it was wetter in the area during the Pleistocene and may well have sustained a permanent lake, now the area receives less than 15 cm of rainfall a year. The frequency of induation of this playa, like most playas, is probably unknown (Lichvar et al. 2004)

Desert Lake
Desert Lake as seen from the dune field looking toward the southwest

There are lots of playas in southern Nevada, but desert is more unique because of its associated sand dunes. To the east of the lake is the Sheep Range, a 1,500-2,000 m mountain range of Cambrian to Devonian dolmite and limestone (Jayko, 2007). Along with predominately westerly winds, this allows the formation of a dune field.

Sheep Range
The Sheep Range from just north of Desert Lake

This process is also illustrated on the larger and more famous Great Sand Dunes National Park. As seen in this image from the park's website, winds blow the deposited sand west until it is again deposited at the base of the mountains. Winds blowing through mountains passes from the east help to pile the sand into dunes. For much more information about the Great Sand Dunes see a recent paper in Geomorphology (Madole et al., 2008).

Sand Dunes
Desert Lake Sand Dune Field

I estimated the tallest dunes as > 20 m. The Dune Field covers only a few square km of land, however, the surrounding area is quite sand, but is mostly covered in vegetation. The dunes themselves are only sparsely vegetated with Ambrosia eriocentra (woolly bursage) and Chilopsis linearis (desert willow). The dune field is one of the northernmost natural occurses of C. linearis (Ackerman, 2003).

Chilopsis linearis
Chilopsis linearis

Finally, just for fun, here is a shot of some ripples on the dunes and check out's recent visit to the Kelso Dunes in California.

Sand Ripples

Ackerman, T. L. 2003. A Flora of the Desert National Wildlife Range, Nevada. Mentzelia 7:1-89.

Jayko, A. S. 2007. Geologic Map of the Pahranagat Range 30' × 60' Quadrangle, Lincoln and Nye Counties, Nevada. US Geological Survey.

Lichvar, R., Gustina, G., Bolus, R. 2004. Ponding duration, ponding frequency, and field indicators: A case study on three California, USA, playas. Wetlands 24:406–413.

Madole, R. F., Romig, J. H., Aleinikoff, J. N., VanStistine, D. P., Yacob, E. Y. 2008. On the origin and age of the Great Sand Dunes, Colorado. Geomorphology 99:99-119.

Posted by Chris M

Animals in the field

Before it was trees, now it is animals in the field. Well I have three, all from eastern Tennessee.

Ruffed Grouse
Ruffled Grouse

Eastern Box Turtle
Eastern Box Turtle

Bear Scat
Ok, this isn't really an animal, just the evidence of one. Black bear scat.