Tuesday, September 30, 2008
This semester I am taking an Advanced Volcanology class focusing on hydrovolcanism. A few weeks back I was preparing a talk for phreatomagmatic fragmentation and I was going to use photos I had taken on previous excursions to the eastern Sierra. Unfortunately, I did not have any photos of what I needed, so with my free weekend camping in Mammoth Lakes sounded great to me.
I stayed in the Twin Lakes campground and spent some time visiting different geologic sites in the area. The first picture was taken from my cot and is called the Dragon's Back, a ridge extending from Mammoth Mountain. The second photo is Twin Falls. If you have never been to the Mammoth Lakes area, the Lake Mary area is an awesome place to camp. There are 6 lakes with several different campground available and Twin Falls is located between Lake Mamie and Twin Lakes. With the activity of Mammoth Mountain in the 1980's, the highest elevation lake in the area, Horseshoe Lake, has been closed due to high levels of carbon dioxide at ground level. The area reminds me of a moon landscape because all plant life has been killed. The third photo is Twin Lake.
Traveling away from the Lake Mary area to the other side of the Mammoth Mountain is Minaret Summit, a place where you can see the Middle Fork of the San Joaquin River drainage, Ritter Range, and take a shuttle down to Devils Postpile National Monument during the summer time. The fourth photo is of the Ritter Range, the mountain peaks in the picture from left to right are Mt. Ritter, Mt. Davis, Rodgers Peak, and Mt. Lyell. The last photo is Mammoth Mountain, which is a major mountain biking and skiing resort destination for the Southern California area. The ski lift is visible at the top of the mountain.
More of the Mammoth Lakes area in the next blog.........
Thursday, September 25, 2008
Once on top, we hiked across to get an aerial view of Chaos Crags considering I was suppose to be completing field work. The 1915 eruptions produced 4 different types of lavas 1) hybrid black dacite 2) andesitic enclaves 3) a banded pumice with dark andesite and light dacite and 4) unbanded light dacite (Clynne, 1999). Sorry, I didn't get extreme close ups of the lavas, I just realized this looking through my photos, darn I will have to hike the trail again. : o ) Instead, I took the artsy approach to photographing the lava.
Wednesday, September 24, 2008
Monday, September 22, 2008
The view above is Lassen Peak from the Devastated Area (northeast of the volcano), named for the mud flow, avalanche, and pyroclastic flow that was released during explosive events on May 19 and 22, 1915. Luckily, no one was killed during these events, but several houses were destroyed along Hat Creek. From prolonged volcanic activity starting in 1914 and lasting to 1917 and the striking natural beauty of the area, Lassen Volcanic National Park was created in 1916.
The above picture is the black dacite lava flow that was erupted on May 19, 1915. This picture was a telephoto shot from the Devastated Area. The flow is more prominent on the southwest side of the volcano.
This feature located on the side of Lassen Peak is just interesting to me. It is called the Vuclan's Eye (this is for the Star Trek fans). I don't know the whole story on how it formed, it looks like some kind of prismatic jointing to me. Any guesses?
So we begin an epic journey up the 2.5 mile trail and over 2,000 ft of evelation gain. This was the second chance I had to hike the trail, but the first chance with amble time to do so. If you ever end up in Lassen Volcanic National Park, Lassen Peak is one of those must do hikes!
Wednesday, September 17, 2008
We spent a good chunk of the day exploring Dome C, looking at enclaves and breaking rocks. Upon investigation, it was hard to tell what rocks were part Dome C and the Chaos Jumbles. It was also hard to find a fresh piece of the host dacite for Dome C, most of the rocks were highly altered. I did find all three types of enclaves, but the fine grained enclaves were not as abundant as the coarse grained and acicular enclaves. Then we headed east for Dome E (below picture).
Dome E was a fairly steep hike, but it was back in the tree line and did not have as many dangerous loose jagged blocks to hike over. There was still abundant enclaves, but many were smaller than a foot. Also this rock appeared harder, or maybe I was just tired from swinging my sledge hammer all afternoon. So we worked until late afternoon and started to head back, by then we over 4 challenging miles from the car. We had a decision to make, go back the way we came and have to climb up and over several large ridges to get back to the Chaos Lake Trail or make a straight line over the Chaos Jumbles and walk along road to get back to the car. So we opted for the last choice and that was still tiring.
This last photo was a beautiful sunset over Manzanita Lake, there was a bunch of people fishing, it was quiet and peaceful and it was a great way to end the day.
Heads up for the last day of field work, it involved the biggest elevation gain of the weekend!
Friday, September 12, 2008
In a previous post, I said the Chaos Jumbles were the result of Dome C collapsing around 300 years ago. When the dome collapsed it traveled down the north slope for several miles, ran up against Table Mountain on the other side of the valley, turned west and came to rest after several more miles. Manzanita Lake formed because the jumbles acted as a dam.
So back to the enclaves that are the key to my project. I really liked this enclave. It has both the medium and fine grained enclaves with host plagioclase. The size of enclaves for the Chaos Jumbles ranged from mm's to one I saw that was 2 ft, but it was the largest one I saw. Most where around a ft or smaller.
Tuesday, September 9, 2008
It has actually been awhile since I last posted a blog and I finally got to my field area. The above picture is after eating lunch in Anderson, CA at a Panda Express. I was laughing at the view, not many fast food joints have such a great view, so I figured the picture was a great way to start out the trip! If you want to know where Lassen Peak is look above my head. I was hoping that Lassen was not going to be busy and it wasn't. The weather was beautiful and the sky a wonderful blue color. So we set up camp and embarked on my reconnaissance trip of my field area.
So when we got there Wednesday afternoon, we didn't really have a plan, so we decided since I had not hiked the Chaos Jumbles in detail, that is what we would do first. A refresher, in case you forgot from previous posts, the Chaos Crags are six dacitic domes, named A-F, with Dome A, the oldest in age. The Chaos Jumbles were the result when Dome C collapsed somewhere around 300 years ago (Heiken and Eichelberger, 1980). For my field work, I am trying to figure out the magma mixing event or events. To do so, I need to look at the enclaves (blobs in the rock not of host origin) and distinguish if there are different types. So far there seems to be three different types present in each of the six domes, but I believe that there might be more variations. I think I will be able to determine this with more field work and Crystal Size Distributions (CSD).
The above picture is a fine-grained porphyritic enclave in the host dacite, as classified by Heiken and Eichelberger, 1980. The enclave is about 1 ft long, the larger crystals are resorbed plagioclase from the host dacite.
Heiken, G., and J.C. Eichelberger, 1980, Eruptions at Chaos Crags, Lassen Volcanic National Park, California; Journal of Volcanology and Geothermal Research, 7, 443-481.
There is still more from the first day, but you have to wait until the next post.