Weathering is the process of decaying rock. There are two
main forms of rock weathering: physical and chemical. Physical weathering can
be caused by frost, pressure, heat, salt, expansion and contraction and root
pressure.
The above diagram shows exactly how the physical processes (pressure, frost, heat and root pressure) occurs within the rock causing decay.
http://home.comcast.net/~rhaberlin/mwstyg.htm
Chemical weathering is caused by hydrolysis (addition of water
breaking chemical bonds), dissolution (dissolve), hydration/dehydration
(addition or subtraction of water to molecules), oxidation (combination with
oxygen creates rust) and moss/ lichens (organisms attached to rock that secrete
acids breaking down rock). While traveling through Yellowstone National Park
many of these processes may be observed.
Look closely at the canyon walls in this image of Yellowstone Canyon. They seem as though they have been painted with reds, yellows and whites. The coloration can be attributed to various different processes of weathering. The trees growing out of the canyon walls can also lead to rock decay.
http://www.beilbyvisualarts.com/id1.html
The brilliant colors of Yellowstone Canyon as well as its formation can be attributed to rock weathering. The red color is due to oxidation, the addition of oxygen to the rock molecules, creating a rust within
the rock and slowly breaking down the individual molecules until they are weakened. The rock of the canyon also decays through root pressure. This occurs when seedlings of the
tree find their way into joints (cracks) within the rock, as the tree gets larger
so does its’ root system this expansion creates pressure pushing apart the joint
until it snaps and breaks off. As the rock decays and breaks off it falls down the slope of the canyon wall and is swept by the rushing river below.
As you look closely at this rock you can see tiny discoloration on the rock called Moss. Also observe tiny finger sized holes in the rock called Alveoli which are formed by salt weathering process.
http://www.iusedtohatebirds.com/2010/07/yellowstone-national-park.html
Moss/lichen and salts can also cause decay in the rock of
Yellowstone National Park. The tiny moss organisms cover around rocks and secrete
acid that breaks down the molecules creating the jagged sides of the rock. Alveoli (tiny holes) are a form of cavernous salt weathering. As salt crystals expand in the pores the surrounding rock weakens and eventually breaks away creating the finger sized cavernous holes.
The above diagram shows exactly how the physical processes (pressure, frost, heat and root pressure) occurs within the rock causing decay.
http://home.comcast.net/~rhaberlin/mwstyg.htm
Look closely at the canyon walls in this image of Yellowstone Canyon. They seem as though they have been painted with reds, yellows and whites. The coloration can be attributed to various different processes of weathering. The trees growing out of the canyon walls can also lead to rock decay.
http://www.beilbyvisualarts.com/id1.html
As you look closely at this rock you can see tiny discoloration on the rock called Moss. Also observe tiny finger sized holes in the rock called Alveoli which are formed by salt weathering process.
http://www.iusedtohatebirds.com/2010/07/yellowstone-national-park.html
