Weathering and Mass Wasting

Yellowstone is not exempt from the forces of weathering that influence change on our landscapes. Joints are important in weathering because they allow for more surface area on which chemical and physical weathering can occur. A prime example of joints is the columnar basalt at Sheepeater Cliff.

These columnar basalt were formed from the contractional cooling of a thick lava flow. The vertical cracks are joints.

 http://volcanoes.usgs.gov/yvo/images/gallery2/gallery_volcanic.php

There are several physical weathering processes. One is pressure release, where pressure is released from quick erosion, causing the shell to pop off in slabs.

                                             At Mammoth Hot Springs

                           http://www.jimgmeiner.com/photos.php?id=110&wid=1247&currentpage=1

Another example of pressure release is at the Hot Springs.

On the left side of the rock, it appears as if pieces of the rock has flaked off in shells. This could be due to pressure release. The smooth, round top surface of the rock is also an example of spheroidal weathering, a form of chemical weathering. 

http://www.public-domain-image.com/nature-landscape/hot-spring/slides/yellowstone-hot-springs.html

Cavernous weathering, which is a type of salt weathering, is also a physical weathering process. This weathering forms alveoli and tafoni.

I was so excited when I came across this picture because I was unsuccessful at finding examples of aveoli or tafoni earlier in my search. This is Obsidian glass found at Obsidian Cliff, which has you can see has pores called alveoli.

http://www.johnwise.com/blog/john/potd/photooftheday_01152010.html

Salt weathering is also present at Minerva Spring and Terrace.

All the white on the sides of the rock is salt. As the salt crystals grow and expand they exert pressure on the surrounding rocks that can weaken and break them.

http://mms.nps.gov/yell/features/mammothtour/minerva.htm

Mammoth Hot Springs also provides a good example of another form of weathering called chemical weathering.

Here is Mammoth The green on the side of the rock is lichen and mosses. These organisms will gradually eat away at and weather the rocks surface from the organic acids and chelation. 

http://www.superstock.co.uk/stock-photos-images/4097-2792

Another form of chemical weathering is oxidation, which we can see at Blood Geyser.

All the red you see here is iron oxide from the reaction of iron bearing minerals in the water with oxygen. When the iron solution drys out, the reddish iron oxide will precipitate, which gives the geyser its name "blood geyser." 

http://www.flickr.com/photos/20977524@N02/3767601231

All these examples show the weathering processes that help to change and break down the beautiful landscape of Yellowstone. Yellowstone is also influenced by mass wasting, which has a huge human impact. In July of 2004, a 90 yard debris flow closed the entrance to the park. Sixteen people and three cars had to be rescued.  

Cars trapped by the debris flow that occurred on a steep, impermeable slope. While the area is transport-limited, the section in which the flow occurred is more weather-limited due to a forest fire that stripped the vegetation. Add two inches of rain and you have the massive, 10 feet deep flow. This particular flow has been called a mudslide by the source but the amount of rock and mud in the picture would classify it actually as a debris flow.

http://wapi.isu.edu/envgeo/EG4_mass_wasting/yellowstone_landslide_2004.htm




Sources:
http://wapi.isu.edu/envgeo/EG4_mass_wasting/EG_module_4.htm
http://wapi.isu.edu/envgeo/EG4_mass_wasting/yellowstone_landslide_2004.htm
http://www.flickr.com/photos/albertocueto/3767601231/in/photostream/
http://volcanoes.usgs.gov/yvo/images/gallery2/gallery_volcanic.php