Rockin’ Science Rocks and Rock Cycle

What is a rock? Mixture of minerals, volcanic glass, organic or other materials. There are three types of rocks: Igneous Metamorphic Sedimentary

Igneous Rocks formed when hot magma cools and hardens. Magma vs. lava – Magma is hot, melted rock material beneath Earth’s surface Lava is magma that reaches the Earth’s surface and flows from volcanoes

Two Types of Igneous Rocks Intrusive – generally contain large crystals, and forms when magma cools slowly beneath Earth’s surface. Extrusive – fine-grained, and forms when magma cools quickly at or near Earth’s surface

Further Classification Another way to identify igneous rocks is by the magma from which they form Basaltic Rocks – igneous rocks that are dense and dark in color. They form from magma that is rich in iron and magnesium, but poor in silica.

Granitic Rocks Igneous rocks that have a lower density than basaltic rocks, and are light in color. Granitic magma is thick, stiff and contains lots of silica.

Andesitic Rocks Igneous rocks that have a mineral composition between basaltic and granitic rocks

Mighty Morphin’ Rocks Metamorphic Rocks

Formation Metamorphic rocks form when heat, pressure, or fluids act on igneous, sedimentary, or other metamorphic rocks. The heat and pressure can change the rocks form, composition, or both.

Heat and Pressure… Rocks beneath Earth’s surface are under great pressure from the layers above them. Temperature also increases with depth. The amount of heat and pressure along with the composition of the rock determines what the metamorphic rock will look like.

Type of Rock Before Type of Rock After (metamorphic) Granite/Igneous Gneiss Sandstone/ Sedimentary Quartzite Limestone/ Marble

Hot Fluids In the presence of hot, water-rich fluids, solid rock can change in mineral composition without having to melt.

Classifying Metamorphic Rocks Foliated rocks - when mineral grains flatten and line up in parallel layers Nonfoliated rocks - when mineral grains grow and rearrange but do not form layers.

Examples of Foliated Rocks…

Examples of Nonfoliated Rocks…

Sedimentary Rocks And the Rock Cycle

Settlement - Sediment Sediments are loose rock fragments, mineral grains, and shell that have been moved by wind, water, ice, or gravity. Sedimentary rocks form when sediments are pressed and cemented together. They often form layers. The oldest layer of rock is on the bottom.

Classification Detrital Chemical Organic

Detrital Made of grains of minerals or other rocks. Other minerals dissolved in water act to cement particles together, and the weight of the sediment above them also squeezes or compacts the layers into rock.

Detrital Rocks

Chemical Rocks Form when mineral-rich water from geysers, hot springs, or salty lakes evaporate. Limestone, rock salt, dolostone

Organic Rocks Rocks made of once living things Chalk, Coal

Rock Cycle