Sedimentar y Rock What are Rocks A rock

Sedimentar y Rock

What are Rocks? A rock is a natural substance that is made up of solid crystals of different minerals that have been fused together into a solid lump. Rocks can be classified by their attributes: • Texture • Hardness • Luster • Color • Size

Sedimentary rocks are formed from broken down bits of other rocks or even from the remains of plants or animals. Sediments can be: • Mud • Clay • Sand • Silt • Gravel • Bones • Shells • Dead organisms • Plant matter

How are Sedimentary Rocks Formed? Over millions of years mountains start to break down. Eventually most of the broken bits of rock end up in streams and rivers that flow down the mountains. These little bits of rocks and sand are called sediments.

How are Sedimentary Rocks Formed? When the water slows down enough, they settle in layers on the bottom of lakes or oceans. Each layer is like a page of a book. One piece of paper is not heavy. But a stack of telephone books is very heavy and squishes anything underneath. Over time the layers of sand mud at the bottom of lakes and ocean turns into rocks called sedimentary rocks. Sedimentary rocks can be formed only where sediments are deposited long enough to become cemented into hard beds or strata.

The major characteristic of sedimentary rock is that it forms layers called strata.

Sedimentary rocks are often rich in fossils. Igneous and metamorphic rocks usually do not contain fossils. WHY ? ? ? The processes that form sedimentary rock (compaction and cementation) are much gentler than the processes that form igneous and metamorphic rock (heat and pressure).

Types of Sedimentary Rocks? There are six main types of sedimentary rocks. 1. Sandstone – soft stone made when sand grains cement together. 2. Shale – clay that has been hardened and turned in rock. If often breaks apart in large flat sections. 3. Limestone – contains many fossils and is made of calcium carbonate and/or very tiny shells.

4. Chalk – a soft, white form of limestone 5. Gypsum – common white or colorless mineral. 6. Conglomerate – rounded rocks like pebbles and boulders cemented together

Sedimentary Rock Facts Sedimentary rocks are very important in helping us to find clues about the Earth’s past. Most of chemical sedimentary rocks come from minerals left behind by evaporated water. Table salt actually comes from a chemical sedimentary rock called halite.