Forces and dynamics - Physical Processes in Earth and Environmental Sciences - page 53

Ice

Ambient
water at 20 º C

Sinking and mixing
cool dense
freshwater at 4 º C

Air

- ∆ r g

- ∆ r g

F

F

Water

r pear / r air = 654;
∆ r = 864kgm -3
F B = -8.49 10 3 N

r pear / r water = 0.85;
∆ r = -150kgm -3
F B = 1.47 10 3 N

-80 kg m -3
∆ r for meltwater : ambient water = + 1.77 kg m -3

∆ r for ice : ambient water =

Fig. 3.24 Buoyant force and Archimedes principle.

Fig. 3.25 Buoyancy in the water/ice system.

Buoyant weight
per unit volume
2.6 10 4 kg

Buoyant weight
per unit volume
1.62 10 4 kg

Mineral grain
density 2,650 kgm -3

Mineral grain
density 2,650 kgm -3

Air

Water

Fig. 3.26 Buoyant weights of mineral grains descending along transport paths in air and water.

-ve Buoyancy
of meltwater

Midocean ridge

Ice

Ocean plate

Ocean

Continent

+ve Buoyancy
of rising magma

Asthenosphere

-ve Buoyancy
of subducting plate

Fig. 3.27 Buoyancy in oceans and ocean plates.