Download PCC Beach Sands Exercise

Sources of Beach Sand
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Beach sands are derived from the breakdown
of rocks (or reefs, etc.) in the surrounding
region.
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THEREFORE, whatever is nearby will create
what is on the beach
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OR, what is in the beach sand MUST also be
in the rocks nearby
Sources of Beach Sand
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In California
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lots of rocks = lots of broken rock bits = lots of bits
of minerals = lots of mineral beach sands
Near Coral Reefs
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Lots of organic material = lots of broken bits of
organic material + closer to beach than other
eroded particles = beach full of coral reef
fragments
Heavy Mineral Sand
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Some minerals heavier than others
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Magnetite, pyrite, galena
Takes energy to move particles
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Larger particles = more energy
Oolitic Sands
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Ooites (aka ooids)
Formation:
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CaCO3 precipitates out of water
Forms a CaCO3 (lime) mud on bottom of the sea
floor
Pieces of mud get ripped up by wave action
Ripped up pieces get rolled into balls by the
gentle waves
Eventually harden into ooites
Beach sands
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Location: Cabo, Baja Mexico
Composition: Shells
Source: lots of shells
(kelp bed, tide pool) just
offshore.
http://www.microscope-microscope.org
Beach sands
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Location: Waianapanapa, Maui
Composition: Basalt
Source: Erosion of
basaltic lava flows which
comprise the island of
Maui
http://www.microscope-microscope.org
Basalt = Black Sand Beaches
Basalt
Black Sand Beach, Hawai’i
Waianapanapa, Maui
http://www.hawaiipictures.com
http://www.microscope-microscope.org
Green Sand
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Olivine common in basalt
Crystals can easily fall out during weathering
Creates a beach of green sand
Beach sands
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Location: Guam
Composition: Olivine
Source: Erosion of
basaltic lava flows
containing lots olivine
http://www.microscope-microscope.org
Olivine = Green Sand Beaches
Olivine
Guam
Green Sand Beach
Papakolea, Hawai’i
http://www.microscope-microscope.org
http://www.hawaiipictures.com
Beach sands
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Location: Huahini, Tahiti
Composition: Coral
Source: Breakdown of
coral reefs just offshore
http://www.microscope-microscope.org
Beach sands
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Location: Ventura, California
Composition: Minerals
Source: Breakdown of
rocks in surrounding area
http://www.gly.uga.edu/railsback/sands/sandsmain.html
Minerals = “Tan” Sand
Beaches
Minerals (quartz, feldspar, hornblend)
Ventura, California
Cabrillo Beach
San Pedro, CA
http://www.gly.uga.edu/railsback/sands/sandsmain.html
S. Leyva 2005