RocksRocks6.E.2.1 Summarize the structure of the Earth, including the layers, the mantle and core based on the relative position, composition and density.

6.E.2.1 Summarize the structure of the Earth, including the layers, the mantle and core based on the relative position, composition and density.

Igneous rocks form when magma cools and hardens.

Igneous from the Latin meaning “Fire formed,” is a rock type that forms from the solidification of a molten mineral solution.

Igneous Rocks

GRANITE(igneous rock)

BASALT(igneous rock)

Igneous rocks are classified according to their origin, texture, and mineral composition.

Origin • Igneous rock may form on or beneath Earth’s surface.• Extrusive rocks form on the Earth’s surface (above ground)

when lava cools quickly to create small crystals.• (Extrusive = Exit/outside)

• Intrusive rocks form inside the Earth (underground) when magma cools slowly to create large crystals.

• (Intrusive = Inside)• The most abundant intrusive rock in continental crust is granite.

Igneous Rocks

Igneous Rocks

Intrusive: Large crystals Extrusive: Small crystals

• Intrusive rocks have larger crystals than extrusive rocks.• Extrusive rocks have a fine-grained or glassy texture.

• Texture refers to the crystal size.• Textures are divided into two main types:

1. Fine-grained = crystals are too small to see (basalt)2. Coarse-grained = crystals are easily visible (granite)

Igneous Rocks

Coarse Grained: Large crystals Fine Grained: Small crystals

• Mineral CompositionLava that is low in silica usually forms dark-colored rocks such as basalt. Magma that is high in silica usually forms light-colored rocks, such as granite.

• Uses of Igneous RocksPeople throughout history have used igneous rock for tools and building materials.

Igneous Rocks

• Sediment is small, solid pieces of material that come from rocks or living things.

• Rocks that are composed of the weathered remains of preexisting rock, or plant and animal remains.

• Most sedimentary rocks are formed through a series of processes: erosion, deposition, compaction, and cementation.

• Horizontal layers called “Beds” separated by “Bedding planes,” are a common feature in sedimentary rocks.

Sedimentary Rocks

• ErosionIn erosion, running water, wind, or ice loosen and carry away fragments of rock.

Sedimentary Rocks

• DepositionDeposition is the process by which sediment settles out of the water or wind carrying it.

• CompactionThe process that presses sediments together is compaction.

• CementationCementation is the process in which dissolved minerals crystallize and glue particles of sediment together.

Sedimentary Rocks

Conglomerate – cemented sand, silt, and pebble sediments.

Sandstone – cemented quartz sand grains. Feels gritty. Unfilled spaces between grains make most sandstones porous and permeable to water.

Sedimentary Rocks

Clastic RocksMost sedimentary rocks are made up of broken pieces of other rocks. A clastic rock is a sedimentary rock that forms when rock fragments are squeezed together.

Organic RocksNot all sedimentary rocks are made from particles of other rocks. Organic rock forms where the remains of plants and animals are deposited in thick layers. “Organic” once were part of living things or were made by living things. Ex.) coal & limestone

Sedimentary Rocks

Types

Chemical RocksWhen minerals that dissolved in a solution crystallize, chemical rock forms. Ex.) Limestone can form when calcite that is dissolved in lakes, seas, or underground water comes out of solution and forms crystals.

Sedimentary Rocks

Uses of Sedimentary Rocks People have used sedimentary rocks through

out history for many different purposes, including building materials and tools.

Sedimentary Rocks

The White House is built of sandstone.

• Metamorphic rocks form from HEAT and PRESSURE changing the original or parent rock into a completely new rock.

• The parent rock can be either sedimentary, igneous, or even another metamorphic rock.

• Every metamorphic rock is a rock that has changed its form.

Metamorphic Rocks

• The word "metamorphic" comes from Greek and means "To Change Form".

Metamorphic RocksFORMATION OF METAMORPHIC ROCK

• The deeper a rock is buried in the crust, the greater the pressure on that rock. Under high temperature and pressure many times greater than Earth’s surface, the minerals in a rock can be changed into other minerals. The rock has become a metamorphic rock.

Metamorphic Rocks

Metamorphic RocksSolid rock can be changed into a new rock by stresses

metamorphic rock

that cause an increase in HEAT

HEAT from the core

that cause an increase in

PRESSURE

Metamorphic Rocks

Types of Metamorphic Rocks Geologists classify metamorphic rocks

according to the arrangement of the grains that make up the rocks.

Foliated RocksMetamorphic rocks that have their grains arranged in parallel layers or bands are said to be foliated.

Nonfoliated Rocks Mineral grains are arranged randomly.

Metamorphic Rocks

Forming Metamorphic Rocks – Great heat and pressure can change one type of rock into another.

Metamorphic Rocks

Uses of Metamorphic Rock Certain metamorphic rocks are important

materials for building and sculpture. Marble and slate are two of the most useful metamorphic rocks.

Metamorphic Rocks

Garden Sculpture

Questions

What type of rocks form when magma cools and hardens? A. It depends on the location. B. Sedimentary C. Metamorphic D. Igneous

Metamorphic rocks form from _____________

and ______________. A. heat, ice B. heat, pressure C. ice, pressure D. water, minerals

What type of rocks are formed from the weathered products of preexisting rocks that have been transported by water, wind, or glaciers? A. Igneous B. Metamorphic C. Sedimentary D. All of the above

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