Figure 3. Layered or stratified rock. As in Figure 2, the small fragments consist mainly of rhyolite and other volcanic rock bits. But an important difference is that the rock shown in the photo has layers in which the fragments have been sorted according to their size. Some layers consist of pebble-sized fragments, while other layers have sand-sized fragments (note lens cap for scale). This sorting indicates that the volcanic debris has been washed down a slope by water and deposited in layers. This type of rock is called a water-laid tuff. These deposits accumulate near active volcanoes, but may have been carried some distance from the volcanic vent.

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Last updated on October 6, 2005

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