Glossary of Terms: O
- Oblique Aerial Photograph
- Photograph taken from a non-perpendicular angle
from a platform in the atmosphere.
- Tilt of the Earth's polar
axis as measured from the perpendicular
to the plane of the Earth's orbit around
the Sun. The angle of this tilt varies
from 22.5 to 24.5° over a 41,000 year
period. Current obliquity is 23.5°.
- Glassy dark colored volcanic rock.
Usually composed of rhyolite.
- Occluded Front
- A transition zone in the atmosphere where
an advancing cold air
mass sandwiches a warm air mass between
another cold air mass pushing the warm air
into the upper atmosphere.
- A body of saline water found occupying all
or part of the Earth's ocean
basins. There are five recognized oceans: the
Atlantic, the Southern
Ocean, the Pacific Ocean, the
Indian Ocean, and the Arctic
- Ocean Basin
- Part of the Earth's outer surface that is
comprised of the ocean
rise, and continental
slope. The ocean basins are filled
with saline water that makes up the oceans.
- Ocean Current
- Large scale horizontal flow of ocean water
that is persistent and driven by atmospheric
- Ocean Floor
- Flat plain found at the bottom of the ocean.
The ocean floor represents the surface of the oceanic
crust. The ocean floor lies between
ridges and the trenches,
usually 5,000 to 7,000 meters below the ocean
surface. Also called the abyssal
- Oceanic Crust
- Basaltic portion
of the Earth's crust that
makes up the ocean
basins. Approximately 5 to 10 kilometers
thick. See sima
- Oceanic Plate
- A rigid, independent segment of the lithosphere composed
of mainly basalt that
floats on the viscous plastic asthenosphere and
moves over the surface of the Earth. The Earth's
oceanic plates are an average 75 kilometers
thick and were formed less than several hundred
million years ago at one of the Earth's mid-oceanic
ridges. Also see continental
- The scientific study of phenomena found in
the world's oceans.
- Ocean Trench
- Deep depression found at the edge of the ocean
floor. Represents area of tectonic
- O Horizon
- Topmost layer of most soils.
It is composed mainly of plant litter and humus.
- Hydrocarbon based liquid commonly found in
the pores of sedimentary rocks of marine origin.
- Old Growth
- Climax forests dominated by late successional species
of trees that are hundreds to thousands of
years old. Examples include virgin uncut forests
of Douglas fir, western hemlock, giant sequoia,
and coastal redwoods located in western North
America. Also see second-growth
- Oligotrophic Lake
- Lake with a low supply of nutrients in
its waters. Also see eutrophic
lake and mesotrophic
- Common silicate mineral found
in rocks formed from mafic
magma. Its chemical composition varies
between Mg2SiO4 and Fe2SiO4.
- Heterotrophic organism that consumes both plants and
other animals as
a source of food. Examples of ominvores include
pigs, raccoons, rats, bears, turtles, monkeys,
and humans. Also see carnivore, herbivore, scavenger,
- Is an inferential
statistical test where the values
for which one can reject the null hypothesis are located entirely
in one side of the center of the probability
- The up and down movement of sediment roughly
perpendicular to a shoreline because
of wave action.
- Open Sea
- That part of the ocean that
extends from the continental
shelf. Compare with coastal
- Open System
- Is a system that
transfers both matter and energy can cross
its boundary to
the surrounding environment. Most ecosystems
are an example of an open system.
- Open Talik
- Is a form of localized unfrozen ground (talik)
in an area of permafrost.
It is open to the ground surface but enclosed
to permafrost below and at its sides.
- The level of an abiotic factor
or condition in the environment within
range at which a species or population
can function most efficiently or with the greatest
positive effect to its physiological or reproductive
- Mechanical device for measuring non-linear
distances on maps.
- Group of cells and tissues that
have a particular function for an organism.
- Is a specialized structure found in cells that
carry out distinct cellular functions.
- (1) Relating to an organism.
- (2) Derived from an organism.
- Organic Matter
- Mass of matter that
contains living organisms or non-living material
derived from organisms. Sometime refers to
the organic constituents
Also see soil
- Organic Soil
- Soil order
(type) of the Canadian
System of Soil Classification. This
soil type is common in fens and bogs.
This soil is mainly composed of organic
matter in various stages of decomposition.
- Any form of life.
- The arbitrary starting point on a graph or
grid coordinate system. Defined by the intersection
of the x and y-axes. Also see false
- The process of mountain building through tectonic
forces of compression and volcanism.
- Orogenic Belt
- A major range of mountains on the continents.
- Uplift of an air
mass because of a topographic obstruction.
Uplift also causes the cooling of the air
mass. If enough cooling occurs condensation can
occur and form into orographic
- Orographic Precipitation
- Is precipitation that forms when air is forced
to rise because of the physical presence of
elevated land. As the parcel rises it cools
as a result of adiabatic expansion at a rate
of approximately 10° Celsius per 1,000
meters until saturation.
The large amounts of precipitation along the
west coast of Canada are due mainly to this
- Map projection that
presents the Earth's surface in two-dimensions
as if it were being observed from a great distance
in space. Distortion of areas and angles becomes
greater as you move from the center of the
projection to its edges.
- Area of exposed bedrock at
the Earth's surface with no overlying deposits
of soil or regolith.
- Outer Core
- Outer region of the Earth's core.
It is believed to be liquid nickel and iron
and has a density of about 11 grams per cubic
centimeter. It surrounds the inner core and has an average thickness
of about 2,250 kilometers.
- The release of gas from cooling molten rock or
the interior of the Earth. Much of the atmosphere's
gaseous constituents, like water vapor, nitrogen,
and argon, came from outgassing.
- Movement of matter, energy,
or information out of a system.
Also see input.
- Glaciofluvial sediments deposited by meltwater streams at
the edge of a glacier.
- Outwash Plain
- A flat or gentle sloping surface of glaciofluvial sediments deposited
by meltwater streams at
the edge of a glacier.
Usually found in close spatial association
- Geologic period that
occurred roughly 438 to 505 million years ago.
During this period, the first fish and fungi species
- Overbank Flow
- Movement of flood waters
outside a stream
channel during period of high discharge.
- Overland Flow
- The topographic movement of a thin film of
water from precipitation to lower elevations.
With time, this water will begin to organizing
its flow into small channels called rills.
The rills converge to form progressively larger
channels until stream
channels are formed. Occurs when the infiltration
capacity of an area's soil has
been exceeded. Also called sheet
flow or runoff.
- Fault produced
by the fracturing of rock in
a fold because
of intense compression.
- A fold in rock layers where one limb is pushed
past the perpendicular. This results in both
limbs having dips in
the same direction.
- Oxbow Lake
- Is portion of abandoned stream
channel filled with stagnant water
and cut off from the rest of the stream.
Oxbow lakes are created when meanders are
cut off from the rest of the channel because
of lateral stream erosion.
- (1) Chemical attachment of free oxygen to
other elements and compounds.
One of the types of chemical
- (2) Loss of an electron during
a chemical reaction from one atom to
- Soil order
(type) of the United
States Natural Resources Conservation Service
Soil Classification System. These soils
are found in moist tropical environments. They
are extremely weathered and
very old. Layers within the profile have accumulations
of mineral oxides and have a lack of base cations available
- Tri-atomic oxygen that exists in the Earth's atmosphere as
a gas. Ozone is highest in concentration in
the stratosphere (10-50
kilometers above the Earth's surface) where
it absorbs the Sun's ultraviolet radiation.
Stratospheric ozone is produced naturally and
helps to protect life from the harmful effects
of solar ultraviolet radiation. Over the last
few decades levels of stratospheric ozone have
been declining globally, especially in Antarctica.
Scientists have determined that chlorine molecules
released from the decomposition of chlorofluorocarbons are primarily
responsible for ozone destruction in the stratosphere.It
is also abundant near the the Earth's surface
in highly polluted urban centers. In these
areas, it forms as a by product of photochemical smog, and is hazardous
to human health.
- Ozone Hole
- Is a sharp seasonal decrease in stratospheric
ozone concentration that occurs over Antarctica
in the spring. First detected in the late 1970s,
the ozone hole continues to appear as a result
of complex chemical reaction in the atmosphere
that involves CFCs.
- Ozone Layer
- Atmospheric concentration of ozone found
at an altitude of 10 to 50 kilometers above
the Earth's surface. This layer is important
to life on the Earth because ozone absorbs
- Another name for the ozone
M. (2006). "Glossary of Terms: O". Fundamentals of Physical Geography,
2nd Edition. Date