Monday, June 10, 2013

En route to my fifth continent

I'm at Chicago O'Hare right now, on a layover between Syracuse and London. Once I get to London I have another flight to Nairobi, Kenya.

I'm joining the science crew of HSPDP, the Hominid Sites and Paleolake Drilling Project. They are making good progress at the first Kenyan location, at Tugen,Hills near Lake Baringo. In fact things are going so well they'll be done before I get there.

I do get to head up to West Turkana to the second location. We'll be working out of a camp and it's so remote there is no phone or Internet.

I'll have lots of new things to blog about when I get back on July 16 (as well as tackling the backlog of posts I have to catch up on from the last year) but in the meantime I encourage you to search for the HSPDP facebook page. You don't need to have a Facebook account to see it, and that's where the best updates and photos are being posted.

Friday, June 7, 2013

Dunes in Death Valley

On our first night in Death Valley, we camped at Stovepipe Wells. It's a wide open campground, one that I wouldn't want to be in during the heat of summer, but it was a perfect starting point for our first day's itinerary.

Early morning at Stovepipe Wells

As you can see from the photo above, it's a sandy part of Death Valley. In fact, just a short drive from the campground (~ 2 miles) are the Mesquite Flat Sand Dunes, so called because of the mesquite trees among the dunes.

The dunes cover a large area, although the highest one is only 100 feet


Sand dunes are formed by wind-blown sand. When the sand supply, wind direction, and velocity change, so does the type of sand dune that forms:
    • Transverse: constant wind direction and large sand supply
    • Barchan (crescent): constant wind direction but limited sand supply
    • Linear (seif): converging winds and limited sand supply
    • Star: variable wind direction
You can tell which way the prevailing winds blow from the shape of the dunes.

The wind blows the sand up the long windward slope and down the steep leeward slope.

This photo is of the steep (leeward) side of the dunes.
I think the stripe of shadow going down the dune on the right side of the picture is where we went dune running.

Assuming that the shadows are on the leeward side, the prevailing winds blow in the direction of the arrows.
These are mainly linear dunes, but the smallest arrow is pointing to a set of barchan dunes.

Google Earth Image of the sand dunes near Stovepipe Wells.
The red star is the approximate location of the Mesquite Flat Sand Dunes carpark.
The black square shows where the map above is located.
The blue lines outline different types of dunes.
The yellow circle shows a star dune.

Walking across sand dunes is difficult, and climbing up them is grinding, but it is worth it to run down the side of a dune and feel a little bit like you are flying... Those of us that chose to do the dune run left our bags and cameras with the spectators in our group. On the way back, I saw a ripple mark in the sand that wasn't made by the wind, it was a snake track. It would turn out to be the closest we came to seeing a snake on our southwest trip (although a couple of us were on a different field trip to Massachusetts in April and we saw a ribbon snake on that trip). Fortunately, one of my friends had a camera, and he took a photo of the snake track.

Snake track. Photo courtesy of Callum McMillan.

The sand dunes are surrounded by mountains.

In my last post  I showed some pictures of sand dunes preserved in the rocks in Australia. Here's one of those photos again, this time annotated to show the wind direction when the dunes formed. 

At least two different sets of dunes preserved in the Mereenie Sandstone in Australia.
The arrows show the paleowind direction.

If you want to know more about how sand dunes form, I encourage you to look at Chapter 16 of Earths Dynamic Systems, found online here.