Saturday, May 22, 2010

Mt. St. Helens Pictures

May 18th was the 30th anniversary of the 1980 eruption of Mt. St. Helens!
Mt. St. Helens erupted prior to my birth, and I actually only saw it once before I turned 16. But, since then, I've been trying to make up for lost time. Living within a few hours of it makes that pretty easy!
These pictures are all from within the last year.

Memorial Day Weekend:
(I can't lie - this sign is always exciting!)

Still snow-covered.

Older flows contain the majority of Washington caves, including the ever-popular Ape Cave, open to tourists in the summer, and Gueller Ice Cave, a personal favorite.

August:
Without the snow, it's much easier to see the effects of the devastation.

Immediately after the eruption, there were large chunks of the mountain's glacier interspersed with this material. When these melted, they left behind hummocks, or piles of volcanic debris, including ash and large blocks from the cryptodome (the bulge.) The orange coloration is from geothermal alerting before the eruption - as they were heated and exposed to heated water and gases, the chemistry was altered.

Here you can see two different types of lava that were being mixed together when they erupted.

Spirit Lake: Even to this day, there's a layer of logs on the surface of the lake. They float around the lake when the wind blows.

September:
The wind picking up ash on the crater.

The lava domes! The old one is in the foreground, the new one in the background. Should you decide to climb Mt. St. Helens as a tourist, you'd hike up the back side, and summit at the crater wall seen in the background.

A concentrated pyroclastic density current near the crater, with hiking staff for scale.

Gas escape pipe in another pyroclastic flow. After the eruption, the gas that was in the flow needed a way to escape, and formed these pipes to the surface.

Spirit Lake, again, as seen from the Pumic Plain

Older uplifted flows

Pumice (with frog for scale)

This is a small hole dug into the pumice plain. You can see the layer of pyroclasic flow, with the pumice that was rafted to the top. Then, immediately on top is the layer of ash deposited from the ignimbrite cloud. (A layer of very fine ash that rose from the pyroclastic flow, then fell after the flow was deposited.)

Debris avalanche deposits are visible here, seen as the triangle of rising ground in the center. On May 18th, there was a 5.1 earthquake that released the largest landslide in history. This landslide released the pressure in the cryptodome, which trigged the eruption, and the pyroclastic flow. The pyroclastic flow traveled faster than the landslide (or debris avalanche) so the debris avalanche deposits are on top of the pyroclastic flow deposits.

When the pyroclastic flow overran a small lake, the water was flash boiled, creating an explosion pit. This one has been subsequently filled by water.

This is a sample of the dacite cryptodome from the 1980 eruption.
This is obviously my favorite.


References: I learned most of this in the class I took last summer, and the brief fieldwork I did with that professor. They were both pretty awesome experiences!

Wednesday, May 19, 2010

Jordan Craters

Unfortunately, my post on Mt. St. Helens isn't quite ready yet - I spent yesterday going to a lecture on geomorphology on Mars at the Northwest Geological Society in Seattle, and have a big test tomorrow to study for. (Those lectures make my month, and this one was really great. And an added perk: the school pays for our gas and the fancy buffet dinner. Swanky!)
In it's stead, here are some pictures from Jordan Craters, a small volcanic area in Eastern Oregon.

"The 27-square mile olivine basalt lava flow is estimated to be between 4000 and 9000 years old, based on the degree of lichen development on the rocks. An 18-acre flow within the field is thought to be less than 100 years old because not even lichens have begun to colonize."

It's fairly petite, as lava fields go, but really cute. (Bonus: the surrounding countryside is gorgeous.) This picture encompasses about half of the lava field. The foreground is a line of spatter cones. In the mid-ground, you can see the largest of the cinder cones - Coffee Pot Crater. The background are the lava flows themselves.

(Adapted from: Bruce R. Otto and Dana A. Hutchison, The Geology of Jordan Craters, Malheur County, Oregon, The Ore Bin, Vol. 39, No. 8, August 1977)

Coffee Pot Crater, from the rim. The detached wall block is on the right.

These are the reddest scoria I've ever seen - it really resembled raw hamburger at times. In other places, the scoria is a dark black. I hadn't seen this concentration of scoria before, but since it's a cinder cone, scoria is everywhere! It makes climbing out of the crater a bit tortuous.

This is the detached wall block, seen from the side.

The crater floor.


This is the side wall of the crater, with some stratigraphy present.

FYI: There are signs saying that all wheel drive is necessary, but if you're an awesome driver like me, the minivan'll make it.

View Larger Map
Unfortunately, we didn't get to explore the whole lava field, because I had to drop my mum off in Boise because her uncle died unexpectedly. After that, the stalwart minivan died in the deserts of Nevada. But that's another story.

Monday, May 17, 2010

Mt. St. Helens Day tomorrow!



Tomorrow is the 30th anniversary of the May 1980 eruption of Mt. St. Helens!
To say Mt. St. Helens makes me really happy is an understatement.

Wednesday, May 5, 2010

Fort Rock Pictures!


Obligatory Retina Update: My eye is doing well, and I even managed to pass the Driver's Licensing eye test. It only gets tired after studying/being in class for several hours. That makes life a little difficult, but hey, I'm not blind. (!)




These are all from Fort Rock, a really nice tuff ring out in Eastern Oregon. It's the remnants of a volcano that erupted many times through a lake, producing a ring of layered tuff that was then eroded by the lake. I visited there last summer on the way to Jordan Craters (a small lava field with several cinder cones, also in Eastern Oregon.) It was fascinating to learn more about phreatomagmatic (lava + water) eruptions. Also, it was gorgeous!