Glossary - Fundamentals of the Physical Environment - page 889

Glacier A large accumulation of terrestrial ice and superficial snow, metamorphosed
from annual snowfall and other precipitation and capable of deformation and flow
under its own mass.
Glacio - eustatic The change in ocean water volume and global sea level in response to
the growth and decay of ice sheets and glaciers, which has dominated Quaternary
sealevel change.
Glacio - isostatic rebound The isostatic uplift of a land surface formerly supporting an ice
sheet, due to the removal of the weight of ice and eroded rock.
Glaciomarine Said of the interaction between glacier ice, floating shelf-ice, icebergs and
sea water, creating underwater and ice-marginal sediment-landform associations.
Glaciomarine sediment Rock debris released into the sea from tidewater glaciers ,
floating ice shelves and icebergs .
Glaciotectonic Said of the deformation of ice, bedrock and sediment by glacier ice flow
and consequent fold, thrust and shear structures.
Gleying Soil processes characteristic of wet or waterlogged soils; usually denoted by
bluish-grey colours and reddish mottles, produced by a complex series of oxidation
and reduction reactions.
Global hydrological cycle The global stores and transfers of water in its liquid, solid and
gas phases.
Global Ocean Conveyor A slow, three-dimensional ocean current system transferring
warmer surface and intermediate water polewards, with a return equatorward flow of
deep, cold water (see also thermohaline circulation ).
Gouge Soft, fine-grained debris lining a fault or mineral vein.
Graben A down-faulted rock mass flanked by parallel faults and often forming a
structural valley.
Grade A property of soil structure which describes the strength or stability of soil
aggregate development.
Gradients Changes in environmental conditions along a gradient.
Grain ballistics Collisions between moving and stationary particles in a fluid boundary
layer in which energy transferred to stationary particles moves them horizontally or
entrains them in the flow.
Granite A coarse-grained intrusive igneous rock.
Gravitational energy The potential energy acquired by virtue of an object's distance, or
further displacement away, from Earth's centre; it plays an important role in tectonic
processes in the mantle and crust and in geomorphic processes at the surface.
Gravitational water The class of soil moisture which drains from a saturated soil under
the influence of gravity; it is approximately equivalent to water held in pores larger
than 50 µm diameter.
Gravity The force exerted on any body by Earth's mass and axial rotation; it is an
important endogenetic source of energy for geological and geomorphic processes at or
near Earth's surface.
Greenhouse effect The condition in which Earth's average global temperatures are
normally higher than predicted by radiation laws by virtue of the presence of
substances in the lower atmosphere capable of absorbing outgoing long-wave
radiation.