A2 Mid Ocean Ridge

Question 1

Obduction

Answer 1

a process by which the edge of oceanic crust is scraped onto the continental crust.

Question 2

Multi-beam echo-sounder

Answer 2

sends out up to 100 beams of sound covering an arc up to 10 km wide, allowing wide areas of the sea floor to be covered in one transect of the ship. The profiles are only 100 m apart.

Question 3

Side-scan sonar

Answer 3

towed at depth, sends out sound waves across the sea floor so that a side- view profile of submarine features is obtained. Strong echoes indicate a steep smooth surface facing the instrument; weaker echoes suggest a rough surface.

Question 4

Adiabatic (decompression) melting

Answer 4

rising magma experiences a decrease in pressure. Expansion causes a reduction in temperature with the loss of heat as molecules use energy to move further apart. Melting occurs because the melting point also decreases as the pressure decreases.

Question 5

Mush

Answer 5

a mixture of crystals and melt.

Question 6

Continuous magma chamber

Answer 6

continually produces lava.

Question 7

Discontinuous magma chamber

Answer 7

produces lava periodically, with long periods of inactivity in between when the chamber has solidified.

Question 8

Black smoker

Answer 8

a hydrothermal vent associated with volcanic activity at an MOR. It emits dark clouds of fine sulfide particles.

Question 9

Metasomatism

Answer 9

the hydrothermal alteration of rock.

Question 10

Serpentine

Answer 10

a mineral formed by the hydration of olivine.

Question 11

Serpentinite

Answer 11

a rock made of serpentine.

Question 12

White smokers

Answer 12

cooler hydrothermal vents that emit barium, calcium and silicon. Precipitation of anhydrite and silica gives the white colour.