Rocks

Earth’s Rocky Surface

I. Igneous Rocks

Characteristics of Igneous Rocks

●Igneous rocks may contain crystals, which frequently can be seen by the naked eye.

●Some igneous rocks contain no crystals and appear glassy.

●Igneous rocks may be found in many colors and often show different-colored crystals that are not in bands.

The following are igneous rocks in the collection. Read each characteristic and identify each rock. Write the name of the rock in the table.

Basalt Granite Obsidian Pumice

Igneous Rock Characteristics

Identification of Rock Specimen Were you correct? If not, write the correct rock name.

Igneous Rocks forming Beneath the Surface

When igneous rocks cool slowly under the Earth’s surface, the crystals have longer to grow large.

Which rock probably formed under the Earth’s surface? This rock makes up most of the continent crust and has pink, gray, and dark crystals.

Igneous Rocks forming near the Earth’s Surface

When igneous rocks cool quickly at the Earth’s surface, crystals do not have time to grow or if crystals do grow, they are very small.

Which igneous rock is black and glasslike?

Which igneous rock cooled so quickly that gas bubbles were trapped? This rock is very light weight because of its low density. It is usually light gray.

Which rock is dark gray to black? This rock makes up the ocean crust.

II. Sedimentary Rocks

Characteristics of Sedimentary Rocks

●Most are composed of sediments or fragments of other rocks.

●Some are composed of plant and animal remains and may contain fossils.

●Sedimentary rocks often have distinct parallel layers.

●Sedimentary rocks often appear dull or earthy.

Read each characteristic and identify each rock. Write the name of the rock in the table.

Coal Conglomerate Limestone Shale

Sedimentary Rock Characteristics Identification of Rock Specimen Were you correct? If not, write the correct rock name.

Sedimentary Rocks made of fragments of existing rocks.

Which rock is made of a combination of pebbles cemented together?

Which rock formed from small, sand-sized grains?

Sedimentary Rocks made of Organisms were once Living.

In swamps, trees and plants die and settle into the water. This material may be compressed to form layers of carbon. Which one of these rocks was formed from material deposited in a swamp? This rock is black and lightweight.