.........................................................................................................................................................
Altitude Measurements And Rise In Sea Level
Does A Rise In Sea Level Affect Altitude Measurements?
Mahak
Jalan
Mount Everest, in the
Himalayan range, looms at a height of 8,850 meters and is the highest point on
Earth.
Conversely, the
Mariana Trench is known as the deepest point on Earth, extending to a depth of
an astonishing 10,994 meters.
So, how have people
managed to calculate the height of Everest or the depth of the Mariana trench?
It’s common knowledge
that the surface of the Earth isn’t uniform, so more specifically, what is used
as a reference point for height and depth measurements?
Altitude
Most of you have
heard of the concept of ‘altitude’.
In its geographical
definition, it is a concept used to express the height, and sometimes depth, of
a landmass, mountain, ocean etc.
It is defined as
height above sea level.
The reason that the
water level is taken as baseline is because, technically, there is a single
body of water connected around the globe.
Due to the property
of water to obtain the same level all over, sea level is best suited as the
base for carrying out such measurements.
However, we need to
consider an opposing factor – global warming.
One of the most
profound impacts of climate change is rising sea levels due to the melting of
the polar ice caps.
Does this, therefore,
mean that altitude measurements will change? Will the height of Mt. Everest
decrease, or will the depth of the Mariana Trench increase?
Mean Sea Level (MSL)
Well, to clarify,
although the sea level is constantly changing, these daily, seasonal or yearly
changes do not drastically affect the Mean Sea Level (MSL).
As you can guess from
the name, the MSL is the mean, or average, of the sea level.
Since water levels
are constantly changing, MSL is a measurement calculated after obtaining data
regarding water levels over a period of years and then averaging them out to
obtain a mean value.
Therefore, tiny
changes in water levels do not drastically affect the MSL, but due to the
various sea levels across the world, map makers no longer use MSL as a
reference point today.
Geoid
The sea level is
rather unpredictable, even in the absence of global warming. There are many
factors that cause the sea level to change, like rising and ebbing tides,
weather changes, weather anomalies, etc.
Considering that, it
would be pretty hard – almost next to impossible – to get an accurate, fixed
measurement of any structure. Therefore, the concept of geoid was introduced.
To better understand
this, let’s first go over the facts that we know.
The Earth is not a
perfect sphere; in fact, it is an ellipse.
Secondly, any form of
measurement needs a reference point from which calculations can be made.
Thirdly, the water
level, or sea level, is used as the reference point.
Keeping these things
in mind, a geoid is an imaginary representation of the water level on Earth, a
level that is affected solely by gravity and the movement of Earth’s rotation.
To better picture the
geoid and increase its scope of application, it is assumed that water runs
through everything, even in places that actually have landmass.
If the Earth were
perfectly spherical, or even elliptical, we have mathematical formulae to carry
out such calculations.
Unfortunately, the
surface of the Earth is broken by mountains and trenches, among others, and
water cannot stay in a single, straight line.
Therefore, the
outline of the geoid is undulating or wavy. Geoids are used as reference points
for calculations of depth and height.
The actual surface of
the Earth can be thought of an average between the geoid and the shape of an
ellipse.
Obviously, with
changing conditions, the geoid cannot stay the same forever.
Sometimes, when the
difference is a major one, it is altered to better match the current prevailing
conditions on Earth, thereby affecting altitude measurements minutely.
However, these
changes are not as frequent as what must be done if sea level, or even mean sea
level, were used as reference points.
Mahak Jalan has a BSc
degree in Zoology from Mumbai University in India. She loves animals, books and
biology. She has a general assumption that everyone shares her enthusiasm about
the human body! An introvert by nature, she finds solace in music and writing.
|
Mt. Everest
|
No comments:
Post a Comment