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illite
ice sheet glacier forming a continuous cover over a land surface of (by definition) more than 50000 km 2 . Ice sheets are of considerable thickness and
have the tendency to spread radially under their own weight, being not confined to the underlying topography. During the ice ages large parts of the
northern hemisphere were covered by ice sheets: the Fennoscandian ice sheet
covered Scandinavia and parts of Northern Europe, whereas Northern
America and Greenland were overlain by the Laurentide ice sheet. Compare
ice cap.
ice shelf sheet of thick floating ice attached to a landmass and bounded on the
seaward side by steep cliffs. Is is nourished by snow accumulation and by
seaward extension of land glaciers. Ice shelves form along the polar coasts
(e.g., those of Antarctica and Greenland), some of them extending several
hundred kilometers seaward.
ichnofossil (syn. trace fossil) structure within or on the surface of a sedimentary
rock resulting from biological activity, such as (a) burrows and other excavations (the collective name for this type of structuring is bioturbation), (b)
tracks, trails, footprints, resting marks, (c) evidence of feeding activity, and
(d) trails of fecal pellets. Many ichnofossils are restricted to limited environments and can therefore be used for the interpretation of the environment of sediment deposition.
ichthyology all science concerning fish (~Pisces), including systematics, anatomy, physiology, ethology, and ecology.
ichthyophages ~piscivores.
IDMS Isotope Dilution Mass Spectrometry. The most accurate and often also
most sensitive method for determination of the concentration of a chemical
element in seawater or sediment. A known amount of the element with artificially altered ratio of its stable isotopes is added to the unknown amount
(with known natural isotopic signature) in the sample. Upon extraction and
purification of the element, the isotopic ratio of the mixture is determined
with a mass spectrometer. From this value and the other known values
(amount and isotopic ratio of addition, isotopic ratio and volume of sample)
the unknown concentration is calculated.
IKMT Isaacs-Kidd Midwater Trawl, ~nets.
illite a general term for a group of mica-like clay minerals including glauconite,
consisting of a 2 : 1 layer (~clay minerals) with interlayered K ions. Besides K,
glauconite also contains Na, Ca, Mg, Fe 2 +, and Fe3+. The general formula for
illites is: K 1 -1. 5 AI 4 (Si,Al)s02o(OH)4' Illites are developed under alkaline con-
illite
ice sheet glacier forming a continuous cover over a land surface of (by definition) more than 50000 km 2 . Ice sheets are of considerable thickness and
have the tendency to spread radially under their own weight, being not confined to the underlying topography. During the ice ages large parts of the
northern hemisphere were covered by ice sheets: the Fennoscandian ice sheet
covered Scandinavia and parts of Northern Europe, whereas Northern
America and Greenland were overlain by the Laurentide ice sheet. Compare
ice cap.
ice shelf sheet of thick floating ice attached to a landmass and bounded on the
seaward side by steep cliffs. Is is nourished by snow accumulation and by
seaward extension of land glaciers. Ice shelves form along the polar coasts
(e.g., those of Antarctica and Greenland), some of them extending several
hundred kilometers seaward.
ichnofossil (syn. trace fossil) structure within or on the surface of a sedimentary
rock resulting from biological activity, such as (a) burrows and other excavations (the collective name for this type of structuring is bioturbation), (b)
tracks, trails, footprints, resting marks, (c) evidence of feeding activity, and
(d) trails of fecal pellets. Many ichnofossils are restricted to limited environments and can therefore be used for the interpretation of the environment of sediment deposition.
ichthyology all science concerning fish (~Pisces), including systematics, anatomy, physiology, ethology, and ecology.
ichthyophages ~piscivores.
IDMS Isotope Dilution Mass Spectrometry. The most accurate and often also
most sensitive method for determination of the concentration of a chemical
element in seawater or sediment. A known amount of the element with artificially altered ratio of its stable isotopes is added to the unknown amount
(with known natural isotopic signature) in the sample. Upon extraction and
purification of the element, the isotopic ratio of the mixture is determined
with a mass spectrometer. From this value and the other known values
(amount and isotopic ratio of addition, isotopic ratio and volume of sample)
the unknown concentration is calculated.
IKMT Isaacs-Kidd Midwater Trawl, ~nets.
illite a general term for a group of mica-like clay minerals including glauconite,
consisting of a 2 : 1 layer (~clay minerals) with interlayered K ions. Besides K,
glauconite also contains Na, Ca, Mg, Fe 2 +, and Fe3+. The general formula for
illites is: K 1 -1. 5 AI 4 (Si,Al)s02o(OH)4' Illites are developed under alkaline con-