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Image From: Matthew d'Alessio, USGS
http://education.usgs.gov/schoolyard
| Location: |
Near South Hall, University of California, Berkeley |
| About: |
Zoom into the picture above and you can see four different layers of pavement on top of one another. The small white ruler (which is about 10 cm long) sits on the lowest of these layers. It is very common for layers of pavement to be placed on top one-another because it is cheaper and easier to simply cover up the old pavement than it would be to rip it out. Over time, the layers in this picture have eroded away so that layers that were once covered are now exposed. |
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Copyright Larry Fellows, Arizona Geological Survey
http://www.earthscienceworld.org/imagebank/search/results.html?ImageID=hmwnq6
| Location: |
Grand Canyon National Park, Arizona |
| About: |
The classic "layer-cake" structure of the Grand Canyon. The oldest layers are deposited first. Over time, the layers are buried as new sediment gets deposited on top of the existing layers. Using radiometric dating, scientists have determined that the Kaibab limestone that forms the top layers in the photo is 270 million years old. The Bright Angels shale that shows up as the thick dark layer towards the bottom of the canyon in this photo is 600 million years old. Here, the Colorado River has eroded lots of material while carving the Grand Canyon. Now, we can see all of the older layers that were once buried. |
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Image From: Matthew d'Alessio, USGS
http://education.usgs.gov/schoolyard
| Location: |
Near McCone Hall, University of California, Berkeley |
| About: |
The darker material on the left lies on top of the lighter colored pavement. The darker pavement was added later to cover up the lighter pavement that was cracking (some cracks are visible directly behind the white ruler, which is shown for scale). |
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USGS - HVO
http://hvo.wr.usgs.gov/kilauea/update/archive/2003/Feb/5-14.html
| Location: |
Chain of Craters Road, Hawaiian Volcanoes National Park, Hawaii |
| About: |
Hot lava slowly flows over a road in Hawaii. The road was there for decades before the lava flowed over it. National Park rangers work in the background to move a building to rescue it from the flowing lava. Volcanoes can stay active for millions of years, with each new flow of lava covering up an older flow. The same thing happenend to this road in 2003 -- the road in the picture was built on top of a lava flow that buried an older road in the 1960's that was built on top of a flow several hundred years old. |
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