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Ecology
11/30
Earth’s Surface
What Are Topographic Maps?
• A topographic map is a type
of map that shows elevation.
• Topographic maps are used
by people like hikers and
others who need to know
what the elevation of an area
is.
• So what do these lines
mean? Why are there so
many, and why are they so
crooked?
Contour Lines
• Contour lines connect points of equal elevation. All that means is that
where there's a line, everything on that line is the same height or
altitude.
• Think of it this way, if you had a tub of water with a big rock in it and
you started filling the tub with water but paused every minute to
draw a line where the water had risen to - those lines would be like
contour lines. If you did this for the entire rock, then drained all the
water out, the rock would have lines all over it. If you looked at this
from above, you would see all those lines connecting and forming
circles. A topographic map shows those lines. On most maps these
lines are shown with a light brown color.
Index Contours
• If you were to look at a topographic map, you would realize that
there's not just one line, but many. Each line is a different elevation,
but some of the lines have numbers on them. These are called index
contours. Index contours display the exact elevation of one specific
line.
• Why not just put numbers on every line? Space. There just isn't
enough room on the map to keep putting numbers everywhere, and
it would get awfully cluttered if we did.
Example
• To put this into perspective, imagine
you are somewhere with a big
staircase. Maybe you're at the
Pyramids of Giza or one of those big
concrete sports arenas or any other
place where there's lots of steps.
Imagine you are at the very bottom
of those steps. If you start hiking up
the stairs, the tenth step up would be
painted light brown. Not just in one
spot, the entire step, all the way
across. It would represent 10 feet
high. This would be one of your
contour lines.
Contour interval
• The space between any two lines.
• Contour interval is the distance between any two side-by-side lines.
For example, a contour interval of 10 means you would change
elevation 10 feet up or down by crossing over those lines on the map.
It depends which way you're traveling.
• Every space between every line on that map would be 10 feet of
elevation change, no matter how close or spread out those lines are.
This information will either be printed on the map somewhere or you
can figure it out by looking at the index contours.
Contour Rules
• One different thing about topographic maps: they have rules.
Specifically the contour lines have rules - and every topographic map
follows them:
• 1. Lines cannot cross.
• If two lines crossed, it would actually mean that one location had two different
elevations. While that would be pretty cool, being at two different elevations at the
same time would cause some serious issues with physicists because basically you would
need to be in two different places at one time, and that can't happen.
• 2. Lines form circles around hills or depressions.
• For hills and mountains as you go up in elevation, that circle will get smaller
and smaller like a bull's eye.
Lines can (and often do) get really close to each other. The closer those lines, the
steeper the hill would be. A sheer cliff would have lines all piled up to show that
drastic elevation change, and a gentle slope would have contour lines much more
spread out. See how these lines are all bunched up here? This is a topographic map
that would represent this type of cliff landform.
Elevation
• Elevation, or geometric height, is mainly used when referring to
points on the Earth's surface, while altitude or geopotential height is
used for points above the surface, such as an aircraft in flight or a
spacecraft in orbit, and depth is used for points below the surface.
Relief
• Terrain, or land relief, is the vertical and horizontal dimension of land
surface. When relief is described underwater, the term bathymetry is
used.
• Relief (or local relief) refers specifically to the quantitative
measurement of vertical elevation change in a landscape. It is the
difference between maximum and minimum elevations within a given
area, usually of limited extent.[1] The relief of a landscape can change
with the size of the area over which it is measured, making the
definition of the scale over which it is measured very important.
Because it is related to the slope of surfaces within the area of
interest and to the gradient of any streams present, the relief of a
landscape is a useful metric in the study of the Earth's surface.
Landform
• A landform is a natural feature of the Earth's surface. Landforms
together make up a given terrain, and their arrangement on the
landscape or the study of same is known as topography. Typical
landforms include hills, mountains, plateaus, canyons, valleys, as well
as shoreline features such as bays, peninsulas, and seas, including
submerged features such as mid-ocean ridges, volcanoes, and the
great ocean basins.
Plain
• In geography, a plain is a flat area. Plains occur as lowlands and at the
bottoms of valleys but also on plateaus or uplands at high elevations. In a
valley, a plain is enclosed on two sides but in other cases a plain may be
delineated by a complete or partial ring of hills, by mountains or cliffs.
Where a geological region contains more than one plain, they may be
connected by a pass (sometime termed a gap). Plains may have been
formed from flowing lava, deposited by water, ice, wind, or formed by
erosion by these agents from hills and mountains.
• Plains in many areas are important for agriculture because where the soils
were deposited as sediments they may be deep and fertile, and the
flatness facilitates mechanization of crop production; or because they
support grasslands which provide good grazing for livestock.
Types of plains
•
Structural plains: relatively undisturbed horizontal surfaces of the earth. They are structurally depressed areas of the world that make up some of the
most extensive natural lowlands on the Earth's surface.
•
Erosional plains that have been leveled by various agents of denudation such as running water, rivers, wind and glacier which wear out the rugged surface
and smoothens them. Plain resulting from the action of these agents of denudation are called peneplains (almost plain) while plains formed from wind
action are called pediplains.
•
Depositional Plains formed by the deposition of materials brought by various agents of transportation such as rivers, wind, waves, and glaciers. Their
fertility and economic relevance depend greatly on the types of sediments that are laid down.
•
Depositional Plains are grouped into the following:
•
Alluvial plains, formed by rivers, and may be one of these overlapping types:
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•
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Alluvial plain, formed over a long period of time by a river depositing sediment on its flood plain or bed which becomes alluvial soil. The difference between a flood plain and
an alluvial plain is that the flood plain represents the area experiencing flooding fairly regularly in the present or recently, whereas an alluvial plain includes areas where the
flood plain is now and used to be, or areas which only experience flooding a few times a century.
Flood plain, adjacent to a stream, river, lake or wetland that experiences occasional or periodic flooding.
Scroll plain, a plain through which a river meanders with a very low gradient.
•
Lacustrine plain, a plain that originally formed in a lacustrine environment, that is, as the bed of a lake.
•
Lava plain, formed by sheets of flowing lava.
•
Glacial plains, formed by the movement of glaciers under the force of gravity:
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•
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Sandur (plural sandar), a glacial out-wash plain formed of sediments deposited by melt-water at the terminus of a glacier. Sandar consist mainly of stratified (layered and
sorted) gravel and sand
Till plain, a plain of glacial till that forms when a sheet of ice becomes detached from the main body of a glacier and melts in place depositing the sediments it carries. Till plains
are composed of unsorted material (till) of all sizes.
Abyssal plain, a flat or very gently sloping area of the deep ocean basin
Mountain Range
• A mountain range (also mountain barrier/belt/system) is a geographic
area containing numerous geologically related mountains. A mountain
system or system of mountain ranges, sometimes is used to combine
several geological features that are geographically (regionally) related. On
Earth, most significant mountain ranges are the result of plate tectonics,
though mountain ranges are formed by a range of processes, are found on
many planetary mass objects in the Solar System and are likely a feature of
most terrestrial planets.
• Mountain ranges are usually segmented by highlands or mountain passes
and valleys. Individual mountains within the same mountain range do not
necessarily have the same geologic structure or petrology. They may be a
mix of different orogenic expressions and terranes, for example thrust
sheets, uplifted blocks, fold mountains, and volcanic landforms resulting in
a variety of rock types.
Plateau
• In geology and earth science, a plateau (/pləˈtoʊ/ or /ˈplætoʊ/; plural plateaus or plateaux), also called a high plain or tableland,
is an area of highland, usually consisting of relatively flat terrain that is raised significantly above the surrounding area, often with
one or more sides with steep slopes.
• Formation
• Plateaus can be formed by a number of processes, including upwelling of volcanic magma, extrusion of lava, and erosion by water
and glaciers. Magma rises from the mantle causing the ground to swell upward, in really large, flat areas of rock that are uplifted.
Plateaus can also be built up by lava spreading outward from cracks and weak areas in the crust. Plateaus can also be formed by
the erosional processes of glaciers on mountain ranges, leaving them sitting between the mountain ranges. Water can also erode
mountains and other landforms down into plateaus. Computer modeling studies suggest that high plateaus may also be partially a
result from the feedback between tectonic deformation and dry climatic conditions created at the lee side of growing orogens.[1]
• Classification[edit]
• Plateaus are classified according to their surrounding environment.
• Intermontane plateaus are the highest in the world, bordered by mountains. The Tibetan Plateau is one such plateau.
• Piedmont plateaus are bordered on one side by mountains and on the other by a plain or sea.
• Continental plateaus are bordered on all sides by the plains or seas, forming away from mountains.
• Volcanic plateaus are produced by volcanic activity. The Columbia Plateau in the northwestern United States of America is one
such plateau.
• Dissected plateaus are highly eroded plateaus cut by rivers and broken by deep narrow valleys.
Landform region
• A landform region is a specific area that is made up of the same
major landforms, such as plains, mountains or plateaus. Landforms
can be described as any natural feature that is on the earth's surface.