Geoscience Reference
In-Depth Information
basins noted for marshy conditions and high
salinity.
Lacustrine -
Refers to lakes including the water
body, sediment, plants and animals.
Lagoon -
Deepwater enclosed or partially
opened aquatic system, especially in coastal
delta regions.
Lake Agassiz -
Great proglacial lake in north-
central North America that developed as the
last ice sheet retreated from the region. Con-
sidered to be one of the largest fresh-water
lakes that every existed, it covered substantial
parts of the northern Great Plains in Canada
and the United States.
Laurasia -
Ancient megacontinent consisting of
modern North America and Eurasia during
the Paleozoic. It made up the northern
portion of Pangaea.
Lignite -
Soft, brown coal with density and
carbon content between peat and bituminous
coal.
Lithosphere -
Solid, outer portion of the Earth,
including the upper mantle and crust, averag-
ing about 100 km thick, thinner under oceans
and thicker beneath continents.
Littorina Sea -
Stage in development of the
Baltic Sea when water level rose and the sea
transgressed over surrounding coastal areas
during the middle Holocene.
Little Ice Age -
Prolonged period of cold tem-
perature,
c
.
AD
1200 to 1900, during which
the Earth's climate was 1-2 °C lower than
today (Grove 1988).
Mangrove -
Subtropical and tropical marine
coastal ecosystem dominated by halophytic
trees and shrubs growing in brackish to
saline water. Also called mangal.
Marsh -
Water-saturated, poorly drained area,
intermittently or permanently covered by
water, having aquatic and grasslike vegeta-
tion. In Europe, must have a mineral sub-
strate and lack peat accumulation.
Maunder minimum -
Time interval of reduced
solar output during which sun spots all
but disappeared,
AD
1645-1715, that corre-
sponded with the Little Ice Age.
Medieval climatic optimum -
Time period of
anomalously warm conditions, ca.
AD
700-
1200, known from historical records in
Europe and geological evidence elsewhere.
Mere -
Lake, pond or pool. A marsh or fen. A
levee lake behind a barrier of sediment
carried upstream by the tide. Mainly British
regional usage.
Mesotrophic -
Refers to wetland or water
having an intermediate level of nutrients, in
between eutrophic and oligotrophic.
Minerotrophic -
Peatland whose water origi-
nated from mineral soils or rocks, but some-
times via lakes, streams or ground water. It
may be eutropic, mesotrophic or oligotrophic.
Mire -
Marshy, swampy or boggy ground. Col-
lective term for all peat-forming ecosystems,
including bogs, fens, and swamps of ombro-
tropic and minerotropic types. Used mainly
in Europe.
Mitigation -
Balancing wetland loss due to
development or conversion by restoring,
enhancing or creating another similar wetland
elsewhere. Related to the “no net loss”
wetland policy in the United States.
Monsoon -
Climatic regime of certain continen-
tal areas characterized by heavy summer pre-
cipitation and relatively dry winter conditions,
as in South Asia.
Moor -
German term meaning peatland with
similar usage in England.
Moraine -
Glacial landforms created by deposi-
tion of till and other sediment.
Muck -
Organic-rich soil consisting mainly of
humus; organic matter has decayed beyond
the point of recognition.
Munsell Color -
Quantitative means to describe
color based on hue, value and chroma (or
saturation); widely used in soil science and
other disciplines.
Muskeg -
Large expanse of peatland or bogs,
a term used particularly in Canada and Alaska.
Nacre -
Secretion of aragonite and conchiolin
layers that form pearls and mother of pearl
in mollusk shells.
Neoglaciation -
Last four millennia in which
global climate cooled and glaciers expanded
compared with the preceding mid-Holocene
thermal maximum.
Obligate -
Refers to hydrophytic vegetation that
grows only in wetland conditions (
99%).
Oligotrophic -
Refers to wetland or water that
has low level or dei ciency of nutrients avail-
able for plant growth.
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