.......................... Earth. Characteristics, structure and movements

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.

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".

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.


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.

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.

 

Multiple-choice 2. (Spanish activity. Activity in English is under construction)

Relate pictures with names 2. (Spanish activity. Activity in English is under construction)

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.
Crossword 2. (Spanish activity. Activity in English is under construction)

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