More photos from the field...

An addition to my previous post.

John Day Fossil Beds in central Oregon


Volcanic deposits in North Fork Toutle River, near Mt St Helens.


Western section of Dry Falls, a waterfall formed during the Missoula Floods.

More photographs

I'm not dead yet

Really.

So rather than be an unemployed geoscience type this summer, I decided to be a an unemployed geoscience type that travels. So for the last two months, I have been backpacking in various places in the western US. Here are a few geology influenced pictures.

Cirques, tarns, moraines, and an active rockfall (notice dust cloud on mountain on the left) in John Muir Wilderness, Sierra Mountains.

Sag Pond on San Andreas Fault at the south end of the Carrizo Plain.

Point Reyes headlands.

Lava tube at Lava Beds National Monument.

Isostatic Rebound Hudson Bay

The subject of this month's Accretionary Wedge is "Let's do a time warp". Basically, what past (or future) geologic events would you like to be able to observe.

The geologic event I choose is the isostatic rebound of the Hudson Bay region. At the end of the Pleistocene and the beginning the Holocene, the massive ice sheets covering northern North America began to melt. As the weight of thousands of meters of ice over the Hudson Bay region was removed, the surface began to rise.

As the land continued to rise, new shorelines were repeatedly being formed, as the old shorelines were elevated higher. In some places, over 175 old shorelines ring the present bay level. This is equated to over 300 m over rebound in places. And it is still rising.

If I was in a space ship, watching this event unfold in a few minutes rather than thousands of year, I would see a huge mass of ice melting, followed by a quick jump of the land surface. As time would pass, the speed of the rise would slow down. On the surrounding land surface, almost bare rock surfaces, sweep clean of soil by the glaciers, would slowly become colonized by mosses and lichen. Soil would slowly begin to form, allowing shrubs and trees to gain a foot-hold. Water that would have originally laid on the nearly flat surface, would have started to cut the beginnings of stream channels.

I have reached the present. What does the future hold? The land will continue to rise, in some places still over 100 m. As the climate warms (at least in the relative future), more trees will move even more, as the rate of soil creation increases with the warmer temperatures. Lakes will fill in and drainages patterns will become less deranged.

Map Monday 13: Great Falls of the Columbia

I have been missing a few map Monday for no good reason, so maybe I can get in the grove again.

This week map is of "Great Falls of the Columbia" (aka Celilo Falls). The falls was on the Columbia River, just east of the Dallas on the border of Washington and Oregon. I use "was" because it was drowned by the construction of the Dalles Dam in 1957. The falls themselves are local knickpoints at a layer of basalt (part of the Columbia River Basalt Group).

The actual map is from the Lewis and Clark Expedition. Note the map shows their campsite and portage route around the falls.

The Map is from the David Rumsey collection.

Map Information
Allen, P., Biddle, N., Clark, W., Lewis, M. 1814. Great Falls of the Columbia. from History Of The Expedition Under The Command Of Captains Lewis And Clark, To The Sources Of The Missouri, Thence Across The Rocky Mountains And Down The River Columbia To The Pacific Ocean. Performed During The Years 1804-5-6.