Transcript Rocks - PHS GEOGRAPHY

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
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.pandaprod.cdn.s3.amazonaws.com/media/assets/wgbh/ess05/es
s05_int_rockcycle/index.html
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks2.html
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Rocks/Rocks8.html
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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
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Beneath the surface, MAGMA hardens to form
INTRUSIVE rocks with easily visible (COARSEGRAINED) crystal texture.
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Formed in chambers called:
Batholiths
Laccoliths
Dykes
Sills
Volcanic necks
But all are underground!
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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
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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
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Dark-colored, finegrained, 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
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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
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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
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Light colored, frothy
(many air spaces)
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Same minerals as in
granite, but finer in
grain size
For more about igneous rocks:
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Igrocks/Igro
cks1.html
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
• 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.
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks10.html
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks9.html
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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
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Shale is the most
common
sedimentary rock
Sedimentary rocks
cover about threequarters of the land
surface
For more about
sedimentary rocks:
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks1.html
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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
http://www.absorblearning.com/media/attachment.action?quick=13a&
att=2817
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http://www.absorblearning.com/media/attac
hment.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
INGNEOUS
INTRUSION
(DIKE)
Gneisses are common in the Canadian Shield