.......................... Earth. Characteristics, structure
and movements
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Introduction.
We all know that it is hot in summer and cold in winter, but we wonder
why we see that the answer is not easy. If we look at the first picture
of this subject we are tempted to think that it is simply a matter of
distance from the Sun, but this would mean that, for example, when the
Earth is closest to the Sun would have to be both in the summer hemisphere
North and the South and we all know that it is not, that is when we are
in summer, for example in Argentina are in winter.
The reason is quite
another and that has to do with whether the sun's rays strike the earth's
surface perpendicular, as happens in the summer, where the sun is high,
or falling at an angle, as happens in the winter, in the which the sun
is never as high as in summer. Consider that if fall vertically disperses
its heat energy on a surface smaller than if inclined fall and therefore,
each square centimeter over heated. But Why the solar rays differently
throughout the year? In this chapter you will find the answer to this
and other questions about the stations and on the structure of our planet,
indeed the only celestial body inhabited we know.
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Activities
to be performed. Read the explanations about the size of our planet
and its movements and performs the "Multiple choice Test 2"
and exercise "Relate drawings with two names." Then read the
text on the layers that can be distinguished in our planet and performing
the exercise "Crossword 2".
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1.
Planet Earth. Erra Ti is a spherical planet slightly flattened
at the poles. Its equatorial radius is 6.371km and its polar radius is
less than 14km. Given its distance from the Sun has an average surface
temperature of 20 ° C, which let him keep living, feature not found
in any other known star.
2.
Earth movements. The Earth has a rotation on its axis
making a complete revolution every 23 hours and 56 minutes. Because
this movement is no night and day. It also presents a translational
motion around the Sun giving a full turn every 365.25 days.
For this reason and to avoid gaps, after three years of 365 days there
is a leap year, meaning a year has 366 days (by agreement this
day is February 29). He moves around the Sun at a speed of about 40 km
/ s describing an ellipse in a plane called the ecliptic plane.
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3.
The origin of the seasons. The succession of seasons (spring,
summer, autumn and winter) occurs because the axis
of rotation of the Earth is not perpendicular to the plane of the ecliptic,
but forms with it an angle of about 67 º. Because of this tilt, as
the Earth moves around the Sun varies greatly tilt the solar radiation
in the same area throughout the year, thereby giving rise to periods of
greater heat (when the solar rays more perpendicular on surface) and lower
heat times (when solar raigs more obliquely incident on the surface).
In the picture below you can see how when in the northern hemisphere it
is winter in the southern hemisphere's summer and vice versa.
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Position
1. This is the position of the annual cycle in which the northern
hemisphere get more sunlight and more perpendicular and in the Southern
Hemisphere to get less sun and more oblique. Therefore, in the northern
hemisphere are given the highest temperatures of the year is the summer,
and in the southern hemisphere, are given the lowest, is winter. In
the Northern Hemisphere, the day of the year when the sun's rays more
perpendicular arrive and there is more daylight hours on June 21. It
is the day that begins the summer. Therefore called the summer solstice.
Position
2. In the Northern Hemisphere, after the summer, the day in
which there are so many hours of light and dark is between 22 and 23
September. It is the day that begins this fall. It is called the autumnal
equinox.
Position
3. This is the position of the annual cycle in which the northern
hemisphere get less sun and more oblique, and in which the southern hemisphere
sun come more and more perpendicular. Because of this in the northern
hemisphere are given the lowest temperatures of the year is winter,
and in the southern hemisphere are given the highest, is the summer.
In the Northern Hemisphere, the day of the year when the sun's rays reach
more obliquely and there is less daylight hours on 21 December. It
is the day that begins the winter. It is called the winter solstice.
Position
4. In the Northern Hemisphere, after the winter, the day so
many hours of light and dark is between 20 and 21 March. It is the
day that begins the spring. It is called the spring equinox.
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Multiple-choice
2. (Spanish
activity. Activity in English is under construction)
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Relate
pictures with names 2.
(Spanish
activity. Activity in English is under construction)
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4.
The structure of the Earth. On Earth traditionally there are
four areas of outside to inside are:
1.
Atmosphere. It is the layer of gases (mainly nitrogen and oxygen)
that surrounds the rest of the planet
2.
Hydrosphere. It is the covering layer of water 75% of the planet's
surface. It consists of oceans, seas, rivers and lakes.
3.
Biosphere. Is the area of the atmosphere, the hydrosphere rocky surface
and in which there beings.
4.
Central body rock. It is the huge mass of rocks and magmas that form
the planet. Here are three layers:
Bark.
Surface layer is solid. There are two types of crust:
Oceanic
crust. Is the crust under the oceans, ie which is the ocean
floor. Just a thickness of 7-10 km and is formed by volcanic
rocks, primarily of basalt.
Continental
crust. It's the crust that forms the continents. It has a thickness
of about 40-60 km and basically consists plutòniques rocks,
mainly granite and sedimentary rocks,
mainly clay and limestone.
Mantle.
It is the layer beneath the crust. It consists of silicates of magnesium
and iron. Reaches 2900 km deep and solid areas and areas presents pastoses.
- The surface
layer is solid. Along with the bark is called lithosphere
- The pasty layer
underneath is called asthenosphere.
- The solid layer
beneath the asthenosphere is called mesosphere.
Core.
It is the central portion and therefore the planet also called endosfera.
It is composed of iron (Fe) and nickel (Ni) so that also called Nife.
It has two layers:
- The outer
core is pasty
- The inner
core is solid.
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Crossword
2.
(Spanish
activity. Activity in English is under construction)
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Geology
topics Index
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