Oceanic Crust and Mantle Composition

The video tutorial explains the structure and formation of oceanic crust, focusing on the ophiolite complex. It describes the four distinct layers of oceanic crust: unconsolidated sediments, basaltic lava with pillow structures, sheeted dike complex, and gabbro. The formation process involves magma chambers and seafloor spreading. Additionally, the interaction between seawater and the newly formed crust leads to hydrothermal metamorphism, creating black smokers and metallic deposits.

What is the average thickness of the oceanic crust?

• 20 miles

• 15 miles

• 10 miles

• 5 miles

Which rock type forms the lithospheric mantle beneath the oceanic crust?

• Peridotite

• Granite

• Sandstone

• Limestone

What is the primary composition of the second layer of the oceanic crust?

• Limestone

• Granite

• Pillow basalts

• Sandstone

What is the sheeted dike complex composed of?

• Volcanic ash

• Sedimentary rocks

• Solidified lava

• Interconnected dikes

Where does the basaltic magma that forms new oceanic crust originate?

• From the core

• From the mantle

• From the atmosphere

• From the crust

What is the name given to the tube-shaped structures formed by extruded molten basalt?

• Basaltic columns

• Pillow basalts

• Lava tubes

• Columnar basalts

Which minerals are the first to crystallize in the central magma chamber?

• Quartz and feldspar

• Olivine and pyroxene

• Mica and calcite

• Hematite and magnetite

What process alters the basaltic rock when seawater circulates through the hot crust?

• Physical erosion

• Biological decay

• Hydrothermal metamorphism

• Chemical weathering

What are the particle-filled clouds formed by metallic-rich solutions called?

• White smokers

• Red smokers

• Blue smokers

• Black smokers

What type of deposits are formed when dissolved minerals precipitate from hot seawater?

• Silica deposits

• Metallic sulfide deposits

• Carbonate deposits

• Phosphate deposits