What’s So Special About ROCKS?

Rock Note Guide

ROCKS are….

• A naturally occurring solid mixture of one or more minerals, or organic matter.

Rocks are classified by….

• Texture: the grain size and the way grains fit together

• Visible or no visible grains, shape, pattern, or overall look and feel

• Textures are determined by the environment in which the rock is formed.

• Composition: the minerals or grains found inside the rock

• Whether it was formed in a volcano or alongside a river.

Types of Rocks

• The three main kinds of rock are igneous, sedimentary and metamorphic rock.

• Igneous rock: forms when magma/lava cools and hardens

• Sedimentary rock: forms from organic and inorganic sediments

• Metamorphic rock: forms when existing rock is subjected to great heat & pressure over a long period of time

Igneous Rocks

• Ignis” = Latin for “fire”

• It is also called PORPHYRITIC meaning, it’s a rock that has distinct difference in it’s size of crystals.

• Which these are formed from the cooling of either magma or lava

• The most abundant type of rock

Forms BELOW ground…Intrusive

• Magma cools under Earth’s Surface

• Coarse Grained

• Usually have LARGE crystal grains (due to cooling slowly over a long period of time)

Examples of Intrusive Igneous Rock

Forms ABOVE ground….Extrusive

• Lava cools above Earth’s surface.

• Fined grained

• Usually has SMALL or NO crystals (due to cooling too quickly)

Examples of Extrusive Igneous Rocks

Sedimentary Rocks

• Formed from sediments (rock fragments, mineral grains, animal & plant remains-shells, bones, leaves, stems).

Process to Make Sedimentary Rocks

• 1. Weathering/Erosion: where sediments get broken apart by natural force like wind, water, then transported to a new location.

• 2. Deposition: where sediments get laid down or placed in that new location, then can start accumulating in layers.

• 3. Compaction: where the weight from the layers of sediments forces out fluids and decreases the space between the grains

• 4. Cementation: where minerals dissolved in water crystallize between sediment grains, holding the grains together.

3 Types of Sedimentary Rocks

• Clastic (also called Detrial)—made of broken pieces of other rocks. Formed when rock fragments are squeezed together.

Clastic-Sedimentary Rocks

• Shale: Formed from tiny particles of clay compacted together.

• Sandstone: Forms from the compaction and cementation of small particles of sand.

Clastic-Sedimentary Rocks

• Conglomerate: Formed from fragments of various sizes of rocks and pebbles. Fragments are rounded because they have been worn along riverbeds.

• Breccia: Fragments are jagged with sharp edges. Formed from various size of rocks and pebbles.

Organic—remains of plants and animals are deposited in thick layers

• Organic refers to substances that once were part of living things or were made by living things which contain calcite or calcium carbonate. (Can be tested by using acid)

3 Types of Sedimentary Rocks:

Organic-Sedimentary Rocks

• Coal: Remains of swamp plants buried in water or by volcanic ash.

• Limestone: Formed by hard shells of once living things such as coral, clams, oysters, and snails. When they die their shells pile up and are covered by other sediments compacting and cementing them.

• Chemical—minerals dissolved in lakes, seas, or underground water. Can occur when lakes evaporate.

3 Types of Sedimentary Rocks:

Chemical-Sedimentary Rocks

• Rock Salt: Made of the mineral halite.

• Gypsum: Formed by evaporation in dry climates.

• Rocks that have changed due to intense temperature and pressure

• “Meta” means “change” and morphosis means “form” in Greek

• Igneous, sedimentary and other metamorphic rocks can change to become metamorphic rocks

Metamorphic Rocks

What occurs in the Earth to change these rocks?

• Pressure from overlying rock layers

• High heat, but not enough to melt the rock

• Rocks may be flattened or bent or atoms may be exchanged to form new minerals.

Where do metamorphic rocks usually form?

• Where magma intrudes relatively cool rock

• Near colliding plates (near mountain ranges)

• Places that are covered miles thick with other rock causing pressure

• When hot water intrudes rock

• Where a meteorite strikes Earth (rare)

• Where lightning bolts strike rocks (rare)

Classification of Metamorphic Rocks

• Foliated—mineral grains are flattened and line up in parallel bands or layers.

• Example: gneiss formed from rearrangement of minerals in granite into bands

• Examples: Gneiss, Slate, Schist

Classification of Metamorphic Rocks

• Non-Foliated—No bands are formed

• Re-crystalization

• Example: marble formed from limestone

• Other examples: quartzite, Diamonds

Rocks

Transformed Limestone Marble

Shale Slate

Rocks

Transformed Sandstone Quartzite

Mudstone Schist Gneiss or