The video tutorial explores the differences between oceanic and continental crusts, highlighting the composition and features of each. It delves into oceanic features like the Mid-Atlantic Ridge and ocean trenches, explaining their formation through plate tectonics. The significance of turbidity currents is illustrated through the 1929 Grand Banks earthquake study. The formation of atolls above extinct volcanoes is described, and the video concludes with a discussion on continental margins and the age of continents, emphasizing the role of subduction in the absence of old oceanic crust.

What is the primary composition of oceanic crust?

• Limestone

• Basalt and gabbro

• Sandstone

• Granite

What geological feature is found at the center of many oceans?

• Ocean trench

• Volcanic island

• Mid-Atlantic Ridge

• Coral reef

What causes ocean trenches to form?

• Transform faults

• Subduction zones

• Divergent plate boundaries

• Erosion

What is a turbidity current?

• A type of ocean current caused by wind

• A density current composed of sediment and water

• A current caused by the rotation of the Earth

• A surface current driven by temperature differences

What event led to the study of turbidity currents in the 1950s?

• The sinking of a ship

• A major hurricane

• The 1929 Grand Banks Earthquake

• The eruption of a volcano

What did geologists find in the cores collected from the Grand Banks area?

• Coral fragments

• Fossilized fish

• Volcanic ash

• A graded bed of sand

How do atolls form?

• Through volcanic eruptions

• By the accumulation of sand

• Above an extinct volcano as it sinks

• From coral reefs growing on continental shelves

What is the average composition of continental crust?

• Basalt

• Granite

• Sandstone

• Limestone

What characterizes an active continental margin?

• Broad and gentle shelves

• Steep and narrow shelves

• Absence of tectonic activity

• Presence of coral reefs

Why are continents older than oceanic crust?

• Continents are not subject to erosion

• Oceanic crust is constantly being subducted

• Continents are made of harder rock

• Oceanic crust forms from volcanic activity