ROCKSMINERAL MIXTURES

THE ROCK CYCLE

Sedimentary Process

Metamorphism

Melting

Cooling & Crystallization

Metamorphism

MetamorphismSedimentary Process

Sedimentary Process

IGNEOUS SEDIMENTARY MAGMAMETAMORPHIC

Rocks reveal the expanse of geologic time, the composition of Earth's crust and the forces that shape it, past life and environments, even the composition of other planets and the age and formation of the universe.

The Rock Cycle relates the formation of each rock type to the others as a continuous cycle of creation and alteration.

The three main rock types are igneous, sedimentary and metamorphic.

ENDURING UNDERSTANDINGS

What is a rock? A rock is a solid combination of one or more minerals.

All rocks begin as magma.

IGNEOUS ROCK

When magma cools and crystallizes, igneous rock is formed. The rate that magma cools determines the size of the crystals, or the "texture", of igneous rock. Igneous rocks are classified according to their texture & composition.

If the magma cools within the crust where it isinsulated, it takes a very long time to crystallize.This allows time for the mineral crystals to grow very large. An igneous rock with very large crystals issaid to have pegmatitic or phaneritic texture.

If magma reaches the surface, it cools very quickly. This does not give time for crystals to grow large so they remain very small. An igneous rock with microscopic-sized crystals has aphanitic texture.

If magma begins to cool slowly below the surface but then is uplifted to finish cooling quickly, it will have a combination of large and microscopic crystals, and the rock is said to have a porphyritic texture.

If magma cools extremely quickly, as when it erupts intowater, there is no time for crystals to grow and the rock issaid to have amorphous texture.

When magma with a lot of gas cools, gas is trapped within the rock, creating a vesicular texture.

When very hot ash falls to the ground, it "welds" into a rock with pyroclastic texture. It is very light-weight, being made of a volcanic "spun glass".

ENVIRONMENTS FOR THE FORMATION OF IGNEOUS ROCK

IGNEOUS ROCK COMPOSITION

Felsic igneous rocks are rich in feldspar, quartz, and other low density minerals, and are very low in minerals with low melting points like iron and magnesium. Felsic igneous rocks are generally light in color.

Mafic igneous rocks are rich in iron, magnesium and higher density minerals with high melting points, and poorer in silicate minerals. Mafic igneous rocks are darker in color than felsic rocks.

Igneous rock composition depends on the minerals that make up the rock.

BOWEN'S REACTION SERIES

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IGNEOUS ROCK CROSSWORD

SEDIMENTARY ROCK

CLASTIC SEDIMENTARY ROCKS are formed by the weathering of pre-existing rocksinto sediments and the transportation, deposition and lithification of the sediments.

Sedimentary rocks are classified by how they were formed, as either clasic or nonclastic.

Weathering is the breaking down of large rocks into smaller pieces, or "clasts", by ice, running water, wind or biological activity.

2. Transportation is the moving of sediments by running water, glaciers, winds or gravity.

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3. Deposition occurs when the transporting agent loses energy and drops the sediment it is carrying.

Sediment sizeby energy indepositionalenvironment

4. Over time, lithification occurs due to compaction, cementation or both.

THE FORMATION OF COAL

NONCLASTIC SEDIMENTARY ROCKSare formed either chemically or biologically.

Chemically-formed rocksFormed by precipitation of minerals from water onto the sea floor due to oversaturation of that mineral or change in the water temperature.

Carbonates are the most widespread sedimentary rocks, especially limestone, and can form layers hundreds of feet thick.

Chert is formed by the precipitation of silica out of seawater.

Evaporites form when sea water evaporates.

Biologically-formed rocksform from the activities or the remains of living organisms.

Chert can be formed from the remains of micro-organisms called radiolarians or diatoms.

Chalk is formed from the remains of micro-organisms called cocolithophorids.

Sedimentary rock that is at least 30% mega fossils is called fossiliferous limestone.

Rock that is 90% mega fossils is called coquina.

In the deep ocean, microscopic organisms called foraminifera with calcareous shells, die and their remains filter to the bottom forming layers of ooze that turns to limestone.

SEDIMENTARY ROCKS CROSSWORD

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METAMORPHIC ROCK

Metamorphic rocks are formed from pre-existing rocks by intense heat and pressure or by chemical alteration.

Metamorphism is Greek for "changed form".

Metamorphic rocks can relate the intensities, ages and types of metamorphism that have occurred over geologic time.

Foliated metamorphic rocksare formed by intense pressureas from mountain-building.

Nonfoliated metamorphic rocksare formed by intense heat aswithin the Earth, or by chemicalalteration.

TYPES OF METAMORPHIC ROCKS

In foliated metamorphic rocks,partial melting from intensepressure forces the mineralcrystals to align in the samedirection as layers, or "foliations".

In nonfoliated metamorphic rock, intense heat causes partial melting allowing the minerals crystals to grow very large and "weld" together, creating a very hard rock.

Foliated Metamorphic Rocks result when intense pressure causes existing rock to partially melt and fold. When the pressure is released, these "plastic" rocks record the intensity of the pressure.

Slate - crystals aligned flat and parallel; small grained rocks

Phyllite - slightly polished luster; medium thick layers and crystal size

Schist - mineral crystals align in parallel planes; large crystals; sparkly luster

Gneiss - minerals separate into compositional layers; coarse grained, highest metamorphic grade before melting

TYPES OF METAMORPHISM

Regional Metamorphism occurs over a very large area.

Mountain building from tectonic forces create foliated rocks due to directed pressure.

Burial metamorphism creates nonfoliated rocks due to equal pressure from all directions.

Contact metamorphism - very localized

Heat from plutons or under lava flows alters country rock.

Metasomatism - magmatic fluids seep into country rocks, combine to form new minerals; escaping gasses carry ions, forming ore deposits.

Hydrothermal - water seeps through cracks near a shallow pluton, is super-heated and dissolves minerals from surrounding rocks; carries dissolved minerals and deposits on surface.

Shock - impact produces brief, ultra-high pressure, causing broken crystal structures and

high-pressure polymorphs.

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METAMORPHIC ROCKS CROSSWORD

ROCK IDENTIFICATION GRAPHIC ORGANIZER