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Geology Part II The Rock Cycle Rocks: Geologic Profiles Geologic Time

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Presentation on theme: "Geology Part II The Rock Cycle Rocks: Geologic Profiles Geologic Time"— Presentation transcript:

1 Geology Part II The Rock Cycle Rocks: Geologic Profiles Geologic Time
Igneous Sedimentary Metamorphic Geologic Profiles Geologic Time Relative Absolute Radioactive Dating

2 Rocks are minerals? an indefinite mixture of naturally occurring substances, mainly minerals. various combinations of minerals and organic substances range in size from tiny pebbles to mountains. make up the earth’s crust.

3 Rocks are not always solid
As discussed in plate tectonics magma is liquid rock While the composition of this basalt flow have the same composition, the smooth pahoehoe lava was hotter than the jagged aa lava. Soil and clay are other examples of nonsolid rock

4 Igneous Rocks Fire Formed Hardens as magma cools “original rock”
Lava is on the Earth

5 2 types of Igneous Rocks 1. Intrusive cools inside the Earth
Slow cooling= big crystals Ex.granite 2. Extrusive cools outside the Earth Fast cooling = tiny crystals Ex. obsidian

6 Types of Intrusive rocks
Granite is the most common and is referred to as “mountain guts” Diorite – iron and magnesium Gabbro – dark, large crystals Peridotite – green, most of upper crust

7 Yosemite Rock formation http://www. nps
“El Capitan is the largest monolith of granite in the world.” Formed deep underground and then uplifted by plate tectonics and shaped by erosion Age can be determines by radioactive dating

8 Extrusive Igneous Rocks
Basalt – common, hard, dark Andesite – began cooling in crust finished on surface large/small crystals Rhyolite – cooled slowly then fast Pumice – light, spongy look Obsidian – volcanic glass, cools fast

9 Metamorphic Rock Created by 1 of 2 processes
Regional process – most common, heat and pressure over large area Contact – heat and pressure next to magma chambers 2 types: Foliated, Nonfoliated Formed from preexisting rock that has been exposed to high heat and/or pressure Enough to deform but not melt Cannot determine age by relative or absolute (radioactive dating)

10 Foliated “layered” rocks Slate – made from shale
Gneiss – made from granite

11 Nonfoliated No ‘layers’ Marble – made from limestone
Quartzite – made from quartz

12 Sedimentary Rock Formed at the bottom of lakes and oceans by the deposition of sediment (small dust, sand, organic material) that was eroded by wind, water, ice from a preexisting rock. Only 5% of Earth’s crust Time and pressure cement particles to form a new rock

13 Sedimentary rock characteristics Breccia: clastic
Often have layers Often contain fossils Not very strong Can determine relative age by location Top layers are younger Absolute age cannot be determined

14 3 types: Clastic, Chemical, Organic
Clastic: Most common Made of other rocks Particles accumulate and harden in 2 ways Weight of upper layers squeeze out liquids Minerals dissolved in ground water act as cement Weathering is an active process

15 Sandstone – sandsized quartz, variety of colors
Shale – most common, mud, clay, silts

16 Chemical Limestone – 50% calcite from seashells
Coquina – large pieces of shell Chalk – microscopic pieces of shell

17 Halite – hard, created by evaporation
Gypsum – soft, created by evaporation Chert – hard, created by heat

18 Organic Coal – black, coarse, decayed plant life

19 Special Features of Sedimentary Rocks
Layering (bedding) Fossils Geode (minerals in a hole or cavity) Concretions (minerals form around a grain or fossil)

20 Rock Cycle Interactive Review

21 Picture Credits "Copyright 2009 by Andrew Alden,, reproduced under educational fair use.“ DeJuana Aldrich

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