3.3 What features exist in the deep-ocean basins?

abyssal plains

large flat features covering 1/3 of planet (some of the deepest and flattest regions on Earth)

• formed by fine particles of sediment slowly drifting onto the deep-ocean floor

• thick blanket of sediment is produced by suspension settling, covering most irregularities of the deep ocean

volcanic features on abyssal plains

• tablemounts (largest)

• seamounts (middle)

• abyssal hills / seaknolls (smallest)

abyssal hills

one of the most abundant features on the planet

• gently rounded

• created by stretching of crust during creation of new sea floor

• during ice ages: sea level is lowered —> less water and less weight overlying MOR —> increase in # of abyssal hills

abyssal hill provinces

extensive regions covered by abyssal hills

ocean trench

passive margins: cont. rise merges cont. slope and abyssal plain but in conv. active margins, slope descends into a long, narrow, ocean trench

• deep linear scars in the ocean floor, caused by the collision of two plates along convergent plate margins

• landward side of trench rises as a volcanic arc or volcanic mountain range

• deepest parts of the world’s oceans

Pacific Ring of Fire

• occurs along the active margins of the Pacific Ocean

• home to the majority of Earth’s active volacnoes and large earthquakes

What are some differences between a submarine canyon and an ocean trench?

• submarine canyon: formed by turbidity currents, part of cont. slope

• ocean trench = caused by conv. active margins, sea floor destruction happens here