Post on 03-Jan-2016
Density of Sand LabObjective:Compare the density of Hawaiian green sand to NJ sand.
Where does sand come from? What is sand?
Hawaii: Black Sand Beach
Hawaii: Green Sand BeachNJ: Sand Beach
• Sand is made from rock that has been weathered and broken down to sediment or mineral grains.
• Streams and rivers transport sediment from inland to sea.
Density depends on mineral composition – not necessarily rock type.
Rock density depends on the mineral or mineral groups that make up a rock
Dense rocks/sand have minerals composed of “heavy” elementsElements• Iron• Magnesium• Calcium
Minerals•Olivine •Amphiboles•Ca feldspars
• These minerals are dark in color and heavy (dense)
• They are common in ocean crust & mantle
http://whatonearth.olehnielsen.dk/rocks/volcanicrocks.asp
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“Light” Rocks/Sand have a high silica content.
Silica or Silicates are a mineral group made of silicon & oxygen (“light” elements)
Silicate rocks make up most of Earth’s continental crust.
SiO2 - also known as Quartz
Silica minerals are “light”
~ 50 % silica in rocks- High in heavy and dense iron & magnesium minerals
- Dark color: black/gray/green
- Green mineral = olivine; common in mantle.
Hawaiian volcanoes have a deep magma source.
Hawaii sand is mostly made of Basalt Rock (Rock of OCEAN CRUST)
NJ sand is made from rocks of Continental CrustFelsic> 70% silicaLight colored mineralsLess dense.
Oceanic Crust is denser than Continental Crust.
Result: SubductionWhen ocean crust and continental crust collide; oceanic crust sinks back into the mantle. It’s heavier! This creates volcanoes on edges of some continents. (Ring of Fire)
Subduction:https://www.youtube.com/watch?v=ryrXAGY1dmE
Hawaii vs. NJHawaii:• Volcanic island in the
middle of the Pacific Ocean.• Formed over a “hot spot”
where magma comes from deep with Earth.
• Rocks made of basaltic oceanic crust.
• Basalt = less silica; more heavy dark minerals with iron and magnesium
NJ:• Continental Crust• Silica-rich minerals in
rock; light in color and density
• Not volcanic
Hawaii v. NJ