|
Contours
(part 2)
Marjorie Henry, Contributor
Describing
landforms by contours is the specific
objective that I started to discuss
in the last lesson. I stated that
the spacing of the contour lines and
their shapes inform you about the
landform represented on the map. Here
are some more landforms that are indicated
by the shape of the contours. A series
of enclosed contour lines represents
one of several features, namely: a
round-topped hill; conical hill; isolated
hill; plateau; escarpment. Observe
these in the diagrams given below.
A
ROUND-TOPPED HILL
A
CONICAL HILL
(Source:
Elementary Map Reading by Thomas
Pickles)
Note
that for both features the contours
are circular and widely spaced, indicating
a gradual rise to the top. However,
there is a smaller area at the peak
for the conical hill. If a cross section
is drawn for this, it would show a
cone-shaped feature.
In
contrast to the series of contour
lines to represent a round-topped
or a conical hill, sometimes you may
see two or three enclosed contour
lines or even a single enclosed contour
standing out in a lowland area. This
is an isolated hill. It is also called
a knoll and is typical of areas with
limestone rocks. See if you can identify
the knolls in this section copied
from a map of Jamaica. Keep in mind
that a significant portion of the
island is made up of limestone rock.
(Source:
Map Reading for the Caribbean
by John Macpherson)
CONTOURS
OF A PLATEAU
(Source:
Elementary Map Reading by Thomas
Pickles)
A
plateau is defined as an upland area
with steep slopes and a levelled (relatively
flat) summit. In the diagram above,
the contours are closely spaced, indicating
steep slopes. For the small area of
600 feet and over, the top is relatively
flat.
CONTOURs
OF AN ESCARPMENT
(Source:
Elementary Map Reading by Thomas
Pickles)
An
ESCARPMENT is a ridge with a steep
side on one side and a gentle slope
on the other side. A RIDGE is a long,
narrow and fairly sharp-edged strip
of highland. It is also called a CREST
and is the highest part of the escarpment.
The steep slope is called the scarp
slope, and the gentle slope is called
the dip slope. Do you see the difference
in the spacing of the contour lines
for both slopes? On the steep or scarp
slope, the contours are close together
and straighter than on the gentler
dip slope.
As
I had indicated in the previous lesson,
I have discussed some selected landforms
that are likely to be found on the
map extracts that you are given in
the examinations, that is, of Caribbean
territories. Consult any available
textbooks for other landforms. In
the examinations you are simply asked
to identify landforms either in a
specific area or you are asked to
identify named landforms in any section
of the map. In the latter situation,
it is advisable to give a four-figure
grid reference for those landforms
you identify. Sometimes you are asked
to describe the physical features
of the area in relation to other things
like settlement, agricultural activities,
drainage and roads. In the next lesson,
I will discuss the approach to be
applied in doing descriptions.
Marjorie
Henry is an independent contributor.
Send questions and comments to kerry-ann.hepburn@gleanerjm.com
|
