PHS Geography Physical Geography/Natural Disasters Rocks PHS Geography Physical Geography/Natural Disasters

rock is made up of various combinations of minerals which in turn are made up of various combinations of elements there are as many variations of rock as there are combinations of minerals, although some rocks are very simple in their chemical structure, eg., diamonds are pure carbon (an element)

Elements form minerals Minerals form rocks

ROCK CYCLE The diagram in the next slide represents the ROCK CYCLE—a scheme that represents the processes of continuous changes that connect the three major groups of rocks: SEDIMENTARY IGNEOUS METAMORPHIC The category of rock type depends on how the rock was formed

http://pbs. panda-prod. cdn. s3. amazonaws http://pbs.panda-prod.cdn.s3.amazonaws.com/media/assets/wgbh/ess05/ess05_int_rockcycle/index.html

Here is another version of the Rock Cycle http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks2.html

http://www. volcanoworld. org/vwdocs/vwlessons/lessons/Rocks/Rocks8 http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Rocks/Rocks8.html

IGNEOUS ROCKS Form by solidification (crystallization) of melted minerals means "of fire" or "fire made", from the cooling of the molten rock (lava on the surface; magma inside) "intrusive" - made inside the earth's surface "extrusive" - made outside the earth' surface eg., the Shield

INTRUSIVE Beneath the surface, MAGMA hardens to form INTRUSIVE rocks with easily visible (COARSE-GRAINED) crystal texture. Formed in chambers called: Batholiths Laccoliths Dykes Sills Volcanic necks But all are underground!

EXTRUSIVE At the surface, LAVA hardens to form EXTRUSIVE rocks with tiny (FINE-GRAINED) crystals or GLASSY (no crystal) TEXTURES Found in lava fields from volcanic eruptions And underwater volcanic vents

Granite Light-colored, coarse- grained, no pattern Mostly quartz, feldspar, mica, and hornblende Often used for buildings and monuments http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Rocks/Rocks10.html

Basalt Dark-colored, fine- grained, extrusive Formed where lava erupted onto surface Most widespread igneous rocks Found locally in the Palisades along west shore of Hudson River, Connecticut River valley http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Slideshow/Igrocks/Igrock2.html

Gabbro Dark-colored, coarse- grained intrusive Similar composition to basalt—plagioclase feldspar with some pyroxene and olivine http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Slideshow/Igrocks/Igrock8.html

Obsidian Natural volcanic glass Forms when lava cools very quickly Usually dark, but small pieces may be clear Fractures along curved (conchoidal) surface Used as spear and arrow points, knives http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Slideshow/Igrocks/Igrock7.html

Pumice and other igneous rocks Light colored, frothy (many air spaces) Same minerals as in granite, but finer in grain size For more about igneous rocks: http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Igrocks/Igrocks1.html

Sedimentary Rocks Sedimentary rocks may be made of rock fragments—sediments—or by chemical reactions. The classification of sediments is shown below. http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks6.html

Sedimentary rock formed from the products of the decomposition of pre-existing rock or the remains of marine life water does the work erosion and transportation mainly, but wind, ice and gravity are also important sediments laid down in horizontal beds or layers, called "strata"

the pressure of overlying deposits causes sediments to solidify over time into rock- called ‘lithification’ layers may be uplifted and warped (folded) or broken (faulted) by tectonic forces (eg., the West. Cordillera)

The rock that underlies much of extreme southern Ontario is limestone. A local example is seen on the Grand River or the Niagara Escarpment.

Non-clastic rocks form by chemical precipitation (settling out from a solution.) Limestone is made from calcite, chert from quartz, and halite is rock salt. http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks10.html

Clastic rocks–made of cemented sediments—are classified by their grain sizes. http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks9.html

Biologic sedimentary rocks come from the remains of organic matter. The most important of these is coal. Anthracite coal results from the greatest pressure and releases the most energy when burned. Other varieties are bituminous and lignite. “Petrified” (permineralized) wood is another organic rock. http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks11.html

More about sedimentary rocks Shale is the most common sedimentary rock Sedimentary rocks cover about three-quarters of the land surface For more about sedimentary rocks: http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks1.html

Metamorphic Rocks Formed by heat and pressure changing existing rocks REGIONAL METAMORPHIC affects a large area and results from plate tectonics CONTACT METAMORPHISM affects rocks on a local scale, such as “baking” sedimentary rocks next to magma or lava

DIFFERENCES IN INTENSITY OF REGIOAL METAMORPHISM

CONVERGENT PLATE BOUNDARY http://www.absorblearning.com/media/attachment.action?quick=13a&att=2817

CONTACT METAMORPHISM http://www.absorblearning.com/media/attachment.action?quick=139&att=2815 The extreme heat from the magma intrusion ‘bakes’ the rock that it comes in contact with and changes the elemental structure and texture of the rock.

CONTACT METAMORPHISM CONTACT METAMORPHISM INGNEOUS INTRUSION (DIKE)

“Foliated” rocks contain much mica and other rocks that produce layering or banding Gneisses are common in the Canadian Shield

Non-foliated metamorphic rocks include marble, which comes from limestone, and quatzite, which comes from sandstone