Flow, deformation, and transport - Physical Processes in Earth and Environmental Sciences - page 104

lithostatic, causing potentially disastrous consequences for
the drill rig and possible “blowout.” The regional
hydraulic gradient drives the direction of migration of
subsurface fluids like water and hydrocarbon. Pressures in

partially molten rocks of the Earth's upper crust in crustal
magma chambers (Section 5.1) may also vary between
hydrostatic and geostatic values, with obvious implications
for the forces occurring during volcanic eruptions.

Neutral stability for all cases

Ambient fluid
r 1

lockbox
fluid r 2
Conditions r 1 = r 2

open

Mixing by molecular diffusion only

Lower horizontal boundary

Ocean and lakes (unstratified)

Water surface

lockbox
liquid ρ 2
Conditions r 1 < r 2
∆ r = +ve

Ambient liquid
r 1

Descending plume (open ocean
cold convection, ice meltout)

open

Wall jet
descending flow
(bottom water production,
turbidity currents)

Wall jet
(turbidity flow,
thermohaline flow)

Water surface

lockbox
liquid r 2
Conditions r 1 > r 2

Surface jet

Ambient liquid
r 1

open

Rising plume

Ocean ridge
hydrothermal
plumes

∆ r = -ve

Atmosphere (unstratified)

lockbox
liquid r 2
Conditions r 1 < r 2

Ambient gas
r 1

open

Thunderstorm
downdraught

∆ r = +ve

Catabatic wind

Sea breeze front
Cold front

lockbox
liquid r 2
Conditions r 1 > r 2
∆ r = -ve

Ambient gas
r 1

open

Rising plume (thermal)

Fig. 4.5 Buoyancy-driven flows.