Check out these cool layers from one volcanic event! The very bottom is pumice (lava foam that hardens into rock that is mostly air) that has fallen off the outcropping. The next layer (which has names carved into it - the letters are about 2 feet tall) is from a "fall". This means, it fell out of the air during an eruption and piled up. The white line is the finer material. Next, there was an ash "flow" where ash flowed down the mountain over the pumice. It was superheated, and "welded" together into a harder rock. This is why there is an overhang. Within the flow, you can see veins of calcite crystals formed when water flowed through and crystallized some of the minerals. At the very top is basalt. This is typical lava which flowed over the ash and pumice, forming a hard, black layer.
Monday, July 13, 2009
Tumalo Pumice Outcropping
Check out these cool layers from one volcanic event! The very bottom is pumice (lava foam that hardens into rock that is mostly air) that has fallen off the outcropping. The next layer (which has names carved into it - the letters are about 2 feet tall) is from a "fall". This means, it fell out of the air during an eruption and piled up. The white line is the finer material. Next, there was an ash "flow" where ash flowed down the mountain over the pumice. It was superheated, and "welded" together into a harder rock. This is why there is an overhang. Within the flow, you can see veins of calcite crystals formed when water flowed through and crystallized some of the minerals. At the very top is basalt. This is typical lava which flowed over the ash and pumice, forming a hard, black layer.
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