Sedimentary rocks

There are three other important kinds of sedimentary rocks.

A conglomerate has big discrete chunks of other rocks in it. These can be made in streambeds, for example, where pebbles are cemented into the rock matrix.

http://library.thinkquest.org/05aug/00461/conglomerateprint.htm

A breccia is like a conglomerate in that it includes pieces of other rocks. Breccias tend to have more shards and broken pieces in them (as opposed to rounded pebbles). Breccias can be made near volcanic explosions and also impact craters (both of which we'll see later this semester).

http://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/breccia.html

A tuff is a hybrid of sedimentary and igneous. It is a compacted (and solidified) ash flow that came out of a volcano. Tuff is typically very light and crumbly (like other sedimentary rocks), but can have many small vesicles (like igneous rocks). It sometimes has layers, like other sedimentary rocks.

http://geology.about.com/od/more_igrocks/ig/extrusives/Tuff-from-Green-Valley.htm

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