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Glossary of Terms: H
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- Habitat
- Location where a plant or animal lives.
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- Hadean
- Geologic eon that
occurred from 3800 to 4600
million years ago. The Earth's oldest rocks date to the end of this time period.
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- Hadley Cell
- Three-dimensional atmospheric circulation cell
located at roughly 0 to 30° North and South of
the equator. The Hadley cell consists of rising air
(intertropical convergence
zone) at the equator and descending air (subtropical highs) at 30° North and
South.
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- Hail
- Hail is a
solid form of precipitation that has a diameter greater
than 5 millimeters. Occasionally, hailstones
can be the size of golf balls or larger. Hailstones
of this size can be quite destructive. The intense
updrafts in mature thunderstorm clouds
are a necessary requirement for hail formation.
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- Hair Hygrometer
- Hygrometer that
uses the expansion and contraction of hair to determine atmospheric humidity.
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- Half-life
- Time required for one half of the nuclei in a radioisotope to
emit its radiation.
Half-lifes for radioisotopes range from a few millionths
of a second to several billion years.
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- Halite
- Sedimentary
rock created by the chemical precipitation
of sodium and chlorine.
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- Hamada
- A very flat desert area
of exposed bedrock.
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- Hanging Valley
- A secondary valley that enters a main valley at
an elevation well above the main valley's floor.
These features are result of past erosion caused
by alpine glaciers.
Hanging valleys are often the site of spectacular
waterfalls.
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- Hanging Wall
- The topmost surface of an inclined fault.
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- Haploid
- Cell that contains only one set of chromosomes.
Also see diploid.
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- Hardpan
- Impervious layer found within the soil.
It can result from the precipitation of iron, illuviation of clay or
the cementing of sand and gravel by calcium carbonate precipitates.
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- Hawaiian
High
- See Pacific High.
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- Hazard
- Phenomenon which can cause loss of life, injury,
disease, economic loss, or environmental damage.
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- Headlands
- A strip of land that juts seaward from
the coastline.
This feature normally bordered by a cliff.
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- Headwaters
- Upper portion of stream's drainage
system.
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- Heat
- Heat is defined as energy in
the process of being transferred from one object
to another because of the temperature difference
between them. In the atmosphere, heat is commonly transferred
by conduction, convection, advection,
and radiation.
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- Heat Capacity
- Is the ratio of the amount of heat
energy absorbed by a substance compared
to its corresponding temperature rise.
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- Heat Energy
- A form of energy created
by the combined internal motion of atoms in a substance.
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- Heat Island
- The dome of relatively warm air which develops
over the center of urbanized areas.
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- Helical Flow
- Movement of water within a stream that
occurs as spiral flows.
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- Herb
- A nonwoody angiosperm whose
above ground vegetation dies off seasonally.
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- Herbivore
- Heterotrophic organism
that consumes plants for nutrition. Also known as
a primary consumer.
Also see detritivore, omnivore,
scavenger, and carnivore.
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- Heredity
- The transmission of behavioral, physiological and
morphological characteristics from parent to offspring.
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- Heterogeneity
- State of being dissimilar or diverse.
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- Heterosphere
- The upper layer in a two part classification of
the atmosphere based on the general homogeneity
of chemical composition. In this layer, oxygen atoms
and nitrogen molecules dominate and remain constant
in their relative quantities. The heterosphere extends
upward from a height of 80 to 100 kilometers depending
on latitude. Below this layer is the homosphere.
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- Heterotroph
- Organism that must consume energy rich organic
molecules for survival. Energy is released from these
molecules through the chemical process respiration.
Also see carnivores, herbivores,
and detritivores.
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- High Pressure
- An area of atmospheric
pressure within the Earth's atmosphere
that is above average. If this system is on the
Earth's surface and contains circular wind flow
and enclosed isobars it
is called an anticyclone.
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- Histosols
- Soil order
(type) of the United
States Natural Resources Conservation Service Soil
Classification System. This soil is composed
more than 30% organic
matter as a result of saturated environmental
conditions.
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- Holistic
- Concerned with a complete system.
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- Holocene Epoch
- Period of time from about 10,000 years ago to today.
During this period glaciers retreated
because of a warmer global climate. Time of modern
humans.
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- Homeostatic (Homeostasis)
- A constant or non-changing state of equilibrium in
a system despite
changes in external conditions.
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- Homosphere
- The lower layer in a two part classification of
the atmosphere based on the general homogeneity
of chemical composition. In this layer, nitrogen,
oxygen, argon, carbon dioxide, and the trace gases
dominate and remain constant in their relative proportions.
The homosphere extends from the Earth's surface to
a height of 80 to 100 kilometers depending on latitude.
Above this layer is the heterosphere.
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- Horizon
- (1) A surface separating two beds in sedimentary
rock.
- (2) A layer within a soil showing unique pedogenic
characteristics. Four major horizons are normally
found in a soil profile: A, B, C, and O.
- (3) Point at which the visible edge of the Earth's
surface meets the sky.
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- Horn
- Pyramidal peak that forms when several cirques erode a
mountain from three or more sides.
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- Horst Fault
- A fault that
is produced when two reverse
faults cause a block of rock to be push up.
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- Hot Spot
- A volcanic area
on the surface of the Earth created by a rising plume
of magma.
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- Host
- Organism that develops disease from a pathogen or
is being feed on by a parasite.
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- Human Geography
- Field of knowledge that studies human-made features
and phenomena on the Earth from a spatial perspective.
Subdiscipline of Geography.
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- Human-Land Tradition
- Academic tradition in modern Geography that
investigates human interactions with the environment.
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- Humidity
- A general term used to describe the amount of water
vapor found in the atmosphere.
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- Humus
- Dark colored semi-soluble organic substance
formed from decomposition of soil
organic matter.
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- Hurricane
- An intense cyclonic storm
consisting of an organized mass of thunderstorms that
develops over the warm oceans of the tropics. To
be classified as a hurricane, winds speeds in the
storm must be greater than 118 kilometers per hour.
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- Hydration
- A form of chemical
weathering that involves the rigid attachment
of H+ and OH- ions to
the atoms and molecules of a mineral.
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- Hydraulic Gradient
- The slope of the water
table or aquifer.
The hydraulic gradient influences the direction
and rate of groundwater flow.
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- Hydrocarbon
- Organic compound composed primarily of hydrogen
and carbon atoms. An example of a hydrocarbon is methane (CH4).
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- Hydrograph
- A graph describing stream
discharge over time.
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- Hydrologic Cycle
- Model that describes the movement of water between
the hydrosphere, lithosphere, atmosphere,
and biosphere.
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- Hydrology
- Field of physical geography that studies the hydrosphere.
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- Hydrolysis
- Chemical weathering process
that involves the reaction between mineral ions
and the ions of water (OH- and H+), and results in
the decomposition of the rock surface
by forming new compounds, and by increasing the pH of
the solution involve through the release of the hydroxide
ions.
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- Hydrosphere
- The hydrosphere describes the waters of the Earth.
Water exists on the Earth in various stores,
including the: atmosphere, oceans, lakes, rivers, glaciers, snowfields and groundwater. Water moves from one store to
another by way of: evaporation, condensation, precipitation, deposition, runoff, infiltration, sublimation, transpiration, and groundwater flow.
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- Hydrostatic Pressure
- Force caused by water under pressure.
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- Hygrometer
- An instrument for measuring atmospheric humidity.
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- Hygroscopic
- Substances that have the ability to absorb water
and therefore accelerate the condensation process.
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- Hygroscopic Coefficient
- Maximum limit of hygroscopic
water around the surface of a soil particle.
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- Hygroscopic Water
- Water held within 0.0002 millimeters of the surface
of a soil particle.
This water is essentially non-mobile and can only
be removed from the soil through heating.
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- Hyphae
- Thread like structures found on a fungus.
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- Hypothesis
- A tentative assumption that is made for the purpose
of empirical scientific testing. A hypothesis becomes
a theory when
repeated testing and evidence suggests the hypothesis
has a strong chance of being correct.
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- Hypothesis Testing
- Process where an alternative and
a null hypothesis are
statistically tested for the purpose of falsifying a hypothesis.
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Citation: Pidwirny,
M. (2006). "Glossary of Terms: H". Fundamentals of Physical Geography,
2nd Edition. Date
Viewed. http://www.physicalgeography.net/physgeoglos/h.html |
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