Thursday, November 23rd, 2017

* Ice age-A time of extensive glacial activity, when alpine glaciers descended into lowland valleys and continental glaciers spread over the higher latitudes.
* Ice Caps- A perennial ice/snow cover over an extensive area of land or sea, today found only around the two geographic poles.
* Ice Crystals- 1) Hexagonal (6-sided) crystals that form upon the freezing of water, may be in one of several shapes- stars, needles, plates, columns or combinations of these forms. 2) Precipitation in the form of slowly falling, singular or unbranched ice needles, columns, or plates, may be called diamond dust.
* Ice- Planetary scientists use this word to refer to water, methane, and ammonia, which usually occur as solids in the outer solar system.
* Ice sheet- see continental glacier
* Ice sheet-A glacier that forms a continuous cover of ice over areas of 50,000 square kilometers or more and spreads outward under the influence of its own weight. (syn: continental glacier, ice cap)
* Iceberg-A large chunk of ice that breaks from a glacier into a body of water.
* Icefall-A section of a glacier that flows down a steep gradient, so that the ice fractures into numerous crevasses and towering ice pinnacles.
* Igneous rock - A rock that forms when molten rock cools down and crystallizes.
* Igneous rock-Rock that solidified from magma.
* Impermeable- describes a rock material through which water does not pass easily.
* Inclination -The inclination of a planet's orbit is the angle between the plane of its orbit and the ecliptic. The inclination of a moon's orbit is the angle between the plane of its orbit and the plane of its primary's equator.
* Index fossil-A fossil that identifies and dates the layers in which it is found. Index fossils are abundantly preserved in rocks, widespread geographically, and existed as a species or genus for only a relatively short time.
* Index fossils- fossils that help to identify the age of the rock in which they occur; found over a wide geographic area but lived for a relatively short period of time and easy to recognize.
* Indian Summer- A period in mid to late Autumn in the eastern United States and eastern Canada characterized by light winds, clear skies and temperatures which are unseasonably warm during the day and refreshingly chill at night. The period usually begins after the first major frost of the season.
* Industrial mineral-Any rock or mineral of economic value exclusive of metal ores, fuels, and gems.
* Inferior planets -The planets Mercury and Venus are inferior planets because their orbits are closer to the Sun than is Earth's orbit.
* Influent stream-A stream that lies above the water table. Water percolates from the stream channel downward into the saturated zone. (syn: losing stream)
* Infrared Radiation- The long wave, (between 0.8 and 100 micrometers in wavelength) electromagnetic radiation emitted by all objects. Often also referred to as heat radiation. Terrestrial radiation, the radiant heat from the Earth's surface, is a form of infrared radiation. The so-called greenhouse gases readily absorb infrared radiation.
* Inner planets- The four planets closest to the sun (closer than the asteroid belt).
* Insolation- INcoming SOLar radiATION, the solar energy that reaches Earth.
* Intensity (of an earthquake)-A measure of the effects an earthquake at a particular place on buildings and people.
* Intensity- A measure of the effects (damage) of an earthquake at a particular place. Intensity depends not only on the magnitude of the earthquake, but also on the distance from the epicenter and the local geology.
* Intermediate rock-Igneous rock with chemical and mineral composition between those of granite and basalt.
* Internal processes-Earth processes that are initiated by movements within the Earth and those internal movements themselves. For example, formation of magma, earthquakes, mountain building, and tectonic plate movement.
* International Date Line- imaginary line through the Pacific Ocean, roughly following the 180 degree longitude meridian where date changes; travelers moving westward advance the date, travelers moving eastward set back the date.
* Intertidal zone-The part of a beach that lies between the high and low tide lines.
* Intracratonic basins-A sedimentary basin located within a craton.
* Intrusion- The process of emplacement of magma in preexisting rock. Also, the term refers to igneous rock mass so formed within the surrounding rock.
* Intrusive igneous rock-A rock formed when magma solidifies within bodies of pre-existing rock.
* Intrusive rock (plutonic) - igneous rock that forms from slowly cooling magma, below Earth's surface.
* Inversion (atmospheric)-A meteorological condition in which the lower layers of air are cooler than those at higher altitudes. This cool air can remain relatively stagnant and allows air pollutants to concentrate in urban areas.
* Inversion- A layer of air in which the temperature increases with height. Meteorological convention considers temperature decreasing with height as the norm, thus when temperature decreases with height, it is inverted. There are four common causes of a temperature inversion- radiational cooling, advection of warm air over cold air as in frontal situations, advection of warm air over a cold surface such as snow or ice, and subsidence, the sinking of air which is then warmed by compression.
* Ion-An atom that has lost or gained electrons.
* Ion-An atom with an electrical charge.
* Ionic substitution-The replacement of one or more kinds of ions in a mineral by other kinds of ions of similar size and charge.
* Ionosphere -A region of charged particles in a planet's upper atmosphere; the part of the earth's atmosphere beginning at an altitude of about 400 kilometers (25 miles) and extending outward 400 kilometers (250 miles) or more.
* Island arc-A gently curving chain of volcanic islands in the ocean formed by convergence of two plates each bearing ocean crust, and the resulting subduction of one plate beneath the other.
* Isobar- A line that connects points of equal air (barometric) pressure on a weather map.
* Isobar-Lines on a weather map connecting points of equal pressure.
* Isostasy- The vertical readjustment of the surface of the earth due to the addition or removal of weight. Commonly associated with the advance and retreat of glacial ice.
* Isostasy-The condition in which the lithosphere floats on the asthenosphere as an iceberg floats on water.
* Isostatic adjustment-The rising and settling of portions of the lithosphere to maintain equilibrium as they float on the plastic asthenosphere.
* Isotherm- A line that connects points of equal air temperature on a weather map.
* Isotherm-A line on a weather map connecting points of equal temperature.
* Isotopes-Atoms of the same element that have the same number of protons but different numbers of neutrons.

* January Thaw- A period of mild weather, usually following a cold spell, which often occurs in late January in the eastern regions of North America, particularly around the Great Lakes region, New England and the Canadian Maritime Provinces. The thaw is associated with a strong flow of warm air northward from the Gulf of Mexico on southerly winds on the back of a high pressure system.
* Jet Stream- A relatively narrow band of high-speed winds, generally greater than 50 knots (57 mph or 93 km/h), found in the upper troposphere above regions of strong horizontal temperature contrasts such as fronts. The major jet streams are the subtropical jet and the polar jet.
* Jet stream-A relatively narrow, high altitude, fast-moving air current.
* Joint- A surface of fracture in a rock.
* Joint-A fracture that occurs without movement of rock on either side of the break.
* Jovian planet -Any of the four outer, gaseous planets- Jupiter, Saturn, Uranus, and Neptune.
* Jovian planets-The outer planets, Jupiter, Saturn, Uranus, and Neptune which are massive with a high proportion of the lighter elements.

* Kame-A small mound, or ridge of layered sediment deposited by a stream that flows on top of, within, or beneath a glacier.
* Karst topography-A type of topography formed over limestone or other soluble rock and characterized by caverns, sinkholes, and underground drainage.
* Kelvin (K) -Zero K is absolute zero; ice melts at 273 K (0° C, 32° F); water boils at 373 K ( 100° C, 212° F).
* Kepler's laws-Three laws of planetary motion based on the observation that planets orbit the sun in ellipses. Law one-The orbits of planets are ellipses, with the sun at one focus. Law two-An imaginary line from a planet to the sun will sweep over equal areas of the ellipse in equal intervals of time. Law three- A planet's period squared is proportional to A. A is the length of a planet's semi-major axis.
* Kerogen-The solid bitumen in oil shales that yields oil when the shales are heated and distilled; the precursor of liquid petroleum.
* Kettle-A depression in glacial drift created by melting of a large chunk of ice left buried in the drift by a receding glacier. The ice prevents sediment from collecting; when the ice melts a lake or swamp may fill the depression.
* Key bed- a single, widespread rock layer that is easily recognizable; has the same characteristics as an index fossil.(examples: a sedimentary layer with volcanic ash; a thin white layer of iridium-rich clay separating Cretaceous and Tertiary rocks (K-T Boundary) suggests a meteor impact occurred around the time the dinosaurs went extinct) see Marker horizon
* Key bed-A thin, widespread, easily recognized sedimentary layer that can be used for correlation.
* Kilogram (kg) -One kilogram is equivalent to 1,000 grams or 2.2 pounds; the mass of a liter of water.
* Kilometer (km) -One kilometer is equivalent to 1,000 meters or 0.62 miles.
* Kinetic energy- The energy of motion.
* Knot- a speed of approximately 1.85 km/h (1.15 mph) often used to describe wind speed.