THE ROCK CYCLE (see ESRT) is used to show how the rock types are related. it also shows the process that produces each rock type. any rock type can change into any other rock type.

ROCK TYPES Rock a group of minerals bound together.

Rocks are identified by their; 1 – texture the size, shape and arrangement of the mineral grains that make up the rock. 2 – composition (crystals, sediments, fossils).

There are three types of rocks; Igneous. Sedimentary. Metamorphic.

Sedimentary Rock formed by the hardening (compaction) and cementing of layers of sediments. Characteristics; bedding or layering of sediments. rounded grains, clasts, and fragments. fossils. cemented sediments with visible pore spaces. fragments of other rocks.

Igneous Rocks form from the cooling and solidification of liquid rock. Characteristics; crystalline texture. intergrown mineral crystals. random arrangement. polyminerallic composition. glassy texture. rounded gas pores or spaces.

Metamorphic Rock preexisting rocks are changed by heat and pressure. Characteristics; polyminerallic composition. interconnected minerals. layering (foliation) slaty, schistose or gneissic formation (banding) distorted or wavy rock structure. stretched pebbles. high percentage of mica minerals.

ROCKS

Rock a group of minerals bound together. granite coquina porphyry breccia porphyry

Rocks are identified by their; 1 – texture the size, shape and arrangement of the mineral grains that make up the rock. 2 – composition crystals, sediments(grain sizes – cobbles, pebbles sand etc), or fossils.

There are three types of rocks (Rocks are classified according to how they were produced) 1 – Igneous cooling of molten rock material. 2 – Sedimentary mostly sediments that have been cemented together. 3 – Metamorphic Rocks that have been altered by heat and or pressure.

IGNEOUS ROCKS Using ESRT worksheet….p.6

Which intrusive igneous rock could be composed of approximately 60% pyroxene, 25% plagioclase feldspar, 10% olivine, and 5% amphibole? (1) granite (3) gabbro (2) rhyolite (4) basalt

Which igneous rock, when weathered, could produce sediment composed of the minerals potassium feldspar, quartz, and amphibole? (1) gabbro (3) andesite (2) Granite (4) basalt

Formation of Igneous rocks Reference Tables p.6

Igneous Rocks form when a magma or lava cools. minerals form distinct, interlocking grains. Pumice Andesite Obsidian

Magma hot molten rock beneath the Earth’s surface.

magma that reaches the Earth’s surface. Pahoehoe A`a flow Ropy pahoehoe Lava magma that reaches the Earth’s surface. pahoehoe flow, Kilauea Volcano, Hawai`i

Igneous rocks form in two ways; 1. Intrusive (aka Plutonic) rocks. form deep underground. Magma cools slowly. large (>1mm) mineral grains. “Coarse - grained” texture.

2. Extrusive (aka Volcanic) rocks. forms at or near Earth’s surface. Lava cools quickly. little time for mineral grains to form = small grains (<1mm). “Fine - grained” or “glassy” texture.

There are two kinds of magma; 1 - Felsic Magma. silica rich (SiO2). Al rich. magma is thick and slow flowing. Forms light-colored minerals (quartz, K-spar)

2 - Mafic Magma. lower silica content. Ca, Fe, Mg rich. Magma is hotter, thinner, and more fluid. Forms dark-colored minerals (hornblende, pyroxene, Na-plag)

Common Igneous Rocks

1 - Obsidian volcanic glass (granite family). usually dark in color. conchoidal (shell-like) fracture.

2 - Pumice felsic lava that hardened while steam and gases were still escaping. has many air holes in it. sometimes it will float.

3 - Scoria like pumice it is full of holes, scoria is made of denser minerals (it won't float)

Identifying Igneous Rocks

1)Determine the shade of the rock. Light shade (remember pink and red are light in shade). Dark shade (green is dark shade). Intermediate (something between dark and light). diorite

2) Determine the texture of the rock. Coarse - you can see the individual mineral grains. GABBRO GRANITE DIORITE

Fine - you can not see the individual mineral grains. ANDESITE BASALT RHYOLITE

Porphyritic - contains both coarse and fine grains.

Glassy (obsidian)

Vesicular - has holes in it (scoria, & pumice)

3) Use the Earth Science Reference Tables to determine the rock’s name. example) Felsic & Coarse grain

1) Contrast the rate of cooling at A that forms intrusive igneous rock with the rate of cooling at B that forms extrusive igneous rock. slow fast A cools more slowly than B

2) Give the numerical grain-size range that should be placed in the flowchart at C . Units must be included in your answer. 1 mm – 10 mm

3) State one igneous rock that could be placed in the flowchart at D obsidian

4) What is the origin of fine-grained igneous rock? (1) lava that cooled slowly on Earth’s surface (2) lava that cooled quickly on Earth’s surface (3) silt that settled slowly in ocean water (4) silt that settled quickly in ocean water

5) Which igneous rock has a vesicular texture and contains the minerals potassium feldspar and quartz? (1) andesite (3) pumice (2) pegmatite (4) scoria

SEDIMENTARY ROCKS Using ESRT worksheet….p.7

Sedimentary rocks are rocks that form from an accumulation of sediments and/or organic material.

There are three types of Sedimentary rocks; Clastic sediments Chemical precipitates and evaporates Organic biologic origin

1 - CLASTIC SEDIMENTARY ROCKS most sedimentary rocks are clastic. clast - solid sediments weathered from other rocks.

sediment particles or materials formed by the weathering and erosion of rocks or organic materials.

Clasts vary in size from pebbles to microscopic flakes of clay. Reference Tables page 6

Clasts can be moved (transported) by these agents of erosion; wind waves running water, and glaciers. gravity Humans/organisms

Running water collects and moves the greatest amount of sediment. as the clasts bump into one another (abrasion), their edges become rounded and smooth. When the velocity of a stream decreases the materials are deposited (dropped). this occurs when a river flows into a lake or ocean.

Mississippi river delta

During deposition, the sediments become sorted . (sorted - grouped according to particle size) Large particles are deposited first. (close to the shore). Fine particles are deposited last. (far from the shore).

river

coarse river pebbles

coarse river pebbles Conglomerate

coarse river pebbles Conglomerate

coarse sands river pebbles Conglomerate

coarse sands river pebbles Conglomerate Sandstone

coarse sands river pebbles Conglomerate Sandstone

coarse sands river clays pebbles Conglomerate Sandstone

Particle size decreases ----- Sediment sizes: coarse sands river clays pebbles Sed Rock names: Conglomerate Sandstone Shale Particle size decreases -----

Formation of Sedimentary rocks Reference Tables p.6

Method of formation… Existing rock is broken down into sediments by weathering and erosion. Sediments are transported to another location. Sediments are deposited, one layer on top of another. Pressure from overlying sediments compresses and compacts the sediments which may cause them to stick together. Dissolved minerals may settle into the spaces between the clasts and cement the materials together.

Examples of Clastic Rocks (examples; shale, sandstone, conglomerate). conglomerate shale sandstone

2 – CHEMICAL SEDIMENTARY ROCKS liquid water contains dissolved minerals. as the water evaporates, the minerals precipitate (drop out of the water) and form a mass of mineral crystals.

Examples of Chemical rocks. (examples; rock salt, gypsum). Rock salt

3 – ORGANIC SEDIMENTARY ROCKS organic means anything related to living organisms. any rock made by living organisms. any rock mostly composed of material from life forms. may contain fossils.

Examples of Organic rocks. (examples; coal, and limestone) coquina coal

fossil any evidence of former life; remains, impressions, footprints. ammonite

1) Which rock was organically formed and sometimes contains fossilized plant impressions? rock gypsum (2) breccia (3) phyllite (4) coal

2) Which processes most likely formed the shale bedrock found near Ithaca, New York? uplift and solidification burial and compaction (3) heat and pressure (4) melting and recrystallization

3) Dolostone is classified as which type of rock? land-derived sedimentary rock (2) chemically formed sedimentary rock (3) foliated metamorphic rock (4) nonfoliated metamorphic rock

4) Which cross section best shows the pattern of sediments deposited by the stream as it enters the ocean near point Z?

5) Most of the rocks shown were formed by volcanic eruptions and crystallization (2) compaction and/or cementation (3) heat and pressure (4) melting and/or solidification

6) Which two rocks are composed primarily of quartz, feldspar, and clay minerals? (1) rock salt and conglomerate (2) rock salt and breccia (3) sandstone and shale (4) sandstone and limestone

Which table shows the rocks correctly classified by texture?

METAMORPHIC ROCKS slate schist quartzite phyllite gneiss marble

METAMORPHIC ROCKS Using the Earth Science Reference Tables p. 7

METAMORPHIC ROCKS rocks that form from changes in previously existing rocks due to heat and or pressure. banding deformed structure gneiss gneiss

Formation of Metamorphic rocks Reference Tables p.6

Effects of metamorphism on rocks pressure squeezes the grains closer together making the rock more dense and less porous. slate shale

Effects of metamorphism on rocks 2) heat and chemicals rearrange the particles.

Effects of metamorphism on rocks 3) minerals may recrystallize and/or new minerals may form. kyanite staurolite garnet

Effects of metamorphism on rocks 4) pressure may cause distorted structure (the curving and folding of the foliation within the rock).

Foliation - a layered arrangement (minerals are aligned in layers) some metamorphic rocks are foliated. other metamorphic rocks may be banded. (colored bands = banding).

There are two types of Metamorphism; Regional Contact

Regional metamorphism large areas of rock are exposed to intense heat and pressure. occurs during mountain building, folding and faulting.

Rock progression during regional metamorphism slate shale phyllite schist gneiss

Contact Metamorphism occurs when hot magma forces its way into surrounding rock. the heat of the magma bakes the rock that are in contact with it.

Contact Metamorphism the area affected is much less than regional metamorphism (usually less than 100 m). the changes in the rock are less dramatic and foliation usually does not occur.

practice questions

1) The metamorphic rock at location A is most likely (1) marble (3) phyllite (2) quartzite (4) slate

2) Wavy bands of light and dark minerals visible in gneiss bedrock probably formed from the (1) cementing together of individual mineral grains (2) cooling and crystallization of magma (3) evaporation of an ancient ocean (4) heat and pressure during metamorphism

3) Which physical characteristic best describes the rock phyllite? (1) glassy texture with gas pockets (2) clastic texture with angular fragments (3) bioclastic texture with cemented shell fragments (4) foliated texture with microscopic mica crystals

4) The rock shown below has a foliated texture and contains the minerals amphibole, quartz, and feldspar arranged in coarse-grained bands. Which rock is shown? (1) slate (3) gneiss (2) dunite (4) quartzite

5) Bedrock located near Old Forge, New York, would most likely have which characteristics? (1) clastic texture consisting of angular sediments of mostly quartz and feldspar cemented together (2) crystalline texture composed predominantly of gypsum (3) noncrystalline, glassy texture with a dark color (4) foliated texture with mica and feldspar separated into bands

6) Which nonfoliated rock forms only in a zone of contact metamorphism? (1) conglomerate (3) pegmatite (2) hornfels (4) quartzite