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