Why do rocks have different appearances

Ultimately however, if you go far enough back into the history of a metamorphic rock you would find that the first protolith was either a sedimentary or igneous rock. Because all metamorphic rocks form below the surface, for them to become exposed at the surface, they must undergo tectonic uplift and removal of the overlying material by erosion. In this exercise you will examine some common igneous, sedimentary and metamorphic rocks, and learn to classify them.

They have a coarse texture with large mineral grains, indicating that they spent thousands or millions of years cooling down inside the earth, a time course that allowed large mineral crystals to grow.

Alternatively, rocks like basalt and obsidian have very small grains and a relatively fine texture. This happens because when magma erupts into lava, it cools more quickly than it would if it stayed inside the earth, giving crystals less time to form. Obsidian cools into volcanic glass so quickly when ejected that the grains are impossible to see with the naked eye.

This happens when the ejected magma still has gases inside of it so when it cools, the gas bubbles are trapped and end up giving the rock a bubbly texture. An example of this would be pumice.

Any rock type can become any other. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited. Tyson Brown, National Geographic Society. National Geographic Society. For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher.

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Any interactives on this page can only be played while you are visiting our website. You cannot download interactives. Metamorphic rocks start as one type of rock and—with pressure, heat, and time—gradually change into a new type of rock.

Sedimentary rocks are one of three main types of rocks, along with igneous and metamorphic. The following passage provides more detailed information related to this investigation that you may choose to explain to your students.

Sedimentary rocks are formed from sediment, which is solid, loose pieces of rocks in the form of sand, silt, clay, and gravel , or the remains of living things found at the surface of the Earth. Sediment is material that has been eroded and deposited by wind, running water, waves, and ice. Sediment can also form from material left behind by the evaporation of seawater, or the settling of the remains of animals and plants in oceans, lakes, and swamps.

In certain conditions, and over a very long period of time, sediment can become compacted and cemented into sedimentary rock. Sedimentary rock is often found in layers. One way to tell if a rock sample is sedimentary is to see if it is made from grains.

Rocks are mixtures of one or more minerals. Just like the apples, butter, flour, and sugar are the ingredients of apple pie, minerals like quartz, mica, and feldspar are the ingredients of an igneous from the Latin word for fire rock called granite. Here it cools and crystallizes into rock. Metamorphic rocks are rocks that have become changed by intense heat or pressure while forming. In certain conditions these rocks cool and crystallize, usually into bands of crystals. One way to tell if a rock sample is metamorphic is to see if the crystals within it are arranged in bands.

Comparing Rocks. Rock Abrasion. Do Rocks Dissolve? Rivers and Land. Skip to main content. K-5 GeoSource. PDF version Teaching and Learning Focus It is important that your students begin to understand that rocks are made of minerals. Setting the Scene To introduce students to rocks, ask students to gather around a collection of rock samples of different types, sizes and shapes of rocks big chunks of granite, sandstone, limestone, marble, etc.

Have your students brainstorm ideas about how this investigation question could be investigated. Design an experiment that could be used to test the investigation question.

What materials would be needed?