Astronomy of Solar System - Geography

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Geography
Astronomy of Solar System
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Homework questions
Chapter 9.
1. The question requires the main layers of the earth, and the densest layer.
There are three (3) main layers of the earth;
 Core is closest to the center of the earth and is made up of the inner core and outer core.
 Mantle is composed of the lower mantle and upper mantle.
 Crust is the less dense layer made of the oceanic crust and the continental crust.
Out of these three layers, the inner core has the highest density.
2. If the sea floor of Eurasian and North American plates has drifted apart by 60km in a
period of 3.3 million years, how far do they move apart in one year?
Working
Conversion of units: 60 km is equivalent to 60,000,000 mm = 6 x 107 mm
3.3 million years is equivalent to 3,300,000 years= 3.3 x 106 years
If the plates drift apart in 3,300,000 years by 6 x 107 mm, what will be the drift in 1 year?
Drift = 1 year∗6 x 10 ˄7 mm
3.3∗10 ˄6 years = 18.18 mm/year
Therefore, the Eurasian and North American plates move apart by 18.18 mm every year.
3. The question requires the three main sources of the present-day earth’s atmosphere.
The three main sources of the atmosphere are gases (mostly Nitrogen, Oxygen, argon and
carbon), water vapour and dust particles.

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4. In this question, a description is required of how the sun heats the lower part of the
atmosphere in a sequential process.
Since the sun is very hot, it releases short-wave radiant solar energy. A short-wave radiation has
shorter wavelengths and high energy. This radiation travels through space and reaches the earth
surface.
The earth surface and objects on it absorb the solar energy and re-emits it in form of long wave
radiation (infrared light). Due to energy losses, the long wave radiation has lesser energy. This
re-emitted energy by the earth then heats up the lower part of the atmosphere (Abdusammatov).
It should be noted that even clouds and other objects on or near the earth surface also absorbs the
short-wave terrestrial radiation and re-emits it back to the atmosphere. This can be through
radiation, conduction and convection. The heat from sun passes through the atmosphere and
reaches earth’s surface by radiation. The movement of wind transfers heat by convection from
the earth’s surface to the atmosphere, warming it.
5. The question requires an explanation on the effect of greenhouse gases on temperature of
the earth.
Green house gases are able to absorb and emit radiations. The shortwave radiation from the sun
reaches the surface of earth and is re-emitted in form of long waves. The greenhouse gasses then
absorb the heat and re-emits them again increasing the temperature of the atmosphere. Since they
capture the heat from earth’s surface, there is lesser heat leaving from the atmosphere as most of
it is trapped and not released to the space. This accumulation of heat on the atmosphere results
into higher temperatures, a phenomenon called global warming (Kweku).