Rock Unit: Earth and Space Science

Naturally occurring solid mass of mineral.

Can be a singular mineral or an aggregate of multiple minerals.

Rock

What are the 3 types of rocks?

Igneous, Sedimentary, and Metamorphic

Rocks from magma or lava; volcanic eruptions

Igneous Rocks

Rocks made up of sediments, the debris of older rocks

Sedimentary rocks

Rocks changes by heat, pressure, and chemical reactions

Metamorphic

What are the 2 type of igneous rocks?

Intrusive and Extrusive

Rocks that cool or harden near or at the earth’s surface.

Extrusive

Rocks that cool and harden beneath the earth’s surface

Intrusive

Intrusive or Extrusive: Small or no crystals because rock cooled rapidly at low temperatures

Extrusive

Intrusive or Extrusive: Large crystals because rock cooled slowly at higher temperatures

Intrusive

The size, shape, and arrangement of the mineral grains along with the rate of cooling.

What is texture based on?

Which texture is this: rocks which have fewer, large mineral grains.

Coarse-grained

Which texture is this: rocks which have a large number of small mineral grains.

Fine-grained

Which texture is this: no grains because the rock cooled instantaneously. They often form at the upper zone of lava flow and contains holes made by gas bubbles.

Vesicular Texture

Which texture is this: Molten rock ejected into the atmosphere, and rock cools instantaneously. No time to form crystals and results in randomly distributed atoms. An example is obsidian.

Glassy

Which texture is this: A combination of small and large grains due to varied temperature and pressure conditions.

Porphyritic

Which texture is this: Rocks composed of rock fragments produced and ejected by explosive volcanic eruptions. They contain fine ash, molten blobs, or large angular blocks torn from the walls of the volcano.

Pyroclastic

Light or dark coloration: Felsic

Light

Light or dark coloration: Mafic

Dark

Which rock family: Felsic magma, silica rich, lighter in color, less dense.

Granite family

Which rock family: mafic, low in silica, darker color, dense, rich in magnesium and iron

Basalt Family

Which rock family: intermediate family, mixture of felsic and mafic components, and medium colored.

Diorite Family

Features of Which Rock:

-Strata or bed

-bedding plain separate strata

-Contain fossils

Sedimentary

Traces of life which hold important clues of ancient environment, are used as time indicators, and used to match up rocks of the same age found at different places.

Fossils

-Clues to past environments

-Provide information about sediment transport

-Rocks often contain fossils

Importance of Sedimentary Rocks

A wide variety of rock fragments mixed with sand, clay, and mud cemented together.

Fragmental Rocks

What are the three types of sedimentary rocks?

Clastic, Chemical, and Organic

Rocks formed from layered, cemented fragments of rocks, pebbles, sand, mud, or clay.

Clastic Sedimentary Rocks

More gravel size rocks cemented together. (Sediments are round)

Conglomerates/ Puddingstones

More gravel size rocks with angular grains, and indicate that particles were not transported far from the source of deposition.

Breccia

Formed from sand grains cemented together

Sandstone

Hardened, layered mud or clay

Shale or Mudstones

Sedimentary Rocks built from the remains of living things. (Examples: coal, limestone, and chalk)

Organic Sedimentary Rocks

Formed from large mineral deposits after a lake or sea is dried up. Can also be deposits due to evaporated minerals being precipitated/

Chemical Sedimentary Rocks

Layering of different sedimentary rock due to changes in climate and environment over time.

Stratification

When large lumps of foreign rock or material get compacted and cemented into a sedimentary rock.

Concretions

Crystal-filled cavities formed by groundwater travelling through hollowed-out sedimentary rock, depositing the dissolved minerals inside.

Geodes

Rocks produced when pre-existing parent rocks are changed through heat, pressure, and chemical reactions. They are very hard and dense and can have parent rocks from any category of rocks.

Metamorphic Rocks

Rocks near or touching hot magma are changes. They often melt partially or fully, causing the materials to recrystallize and make a different structure and mineral composition.

Contact Metamorphism

Rocks within an area of over 100 sqr kilometers where the pressure and high temperature during mountain building cause large scale deformation.

Regional Metamorphism.

-Most of these rocks form deep within the earth’s crust.

-Minerals can change into other minerals or change in size, shape, or separate into layers.

-Hot liquids and gases from magma might dissolve some minerals and add others.

Properties of Metamorphic Rocks

Makes rocks compact and more dense

Low-grade metamorphism

Causes recrystallization and growth of visible crystals

High-grade metamorphism

-Layered arrangement of mineral grains or structure.

-Minerals separate into layers of alternative dark and light bands.

-Shows cleavage

Foliation

What form of metamorphism is foliation (presence of light and dark bands) related to?

Regional

-Extreme pressure squeezes minerals together to pint in one direction.

-Minerals of different densities separate

2 types of foliation

Fine grain, flat, platy, evident cleavage planes, but solid in color and apearance.

Slate

Coarse grain, scaly, minerals oriented in a certain direction, some separation of minerals apparent

Schist

Coarse grain, alternating light and dark bands of minerals aligned in one direction, separation of minerals complete (looks zebra-striped)

Gneiss

-Has no visible layers

-Deformation in minimal

-Randomly oriented minerals: Pressure was not high enough to orientate or align the minerals.

Non-foliated.

Common Examples of Non-Foliated Minerals

Marble and Quartzite

What is a unique characteristic of marble?

Reaction to Hydrochloric Acid

What appearance do non-foliated rocks tend to have?

Sugary

Medium to coarse-grained, relatively soft (3 of mohs scale) interlocking calcite or dolomite grains. Parent stone is limestone or dolostone.

Marble

Medium to course-grained, very hard, massive, fused quartz grains

Quartzite.