Earth-The blue planet
In the beginning, the Earth was an incandescent mass that slowly began to cool, allowing the continents to emerge and acquire their current form. Although many drastic changes took place during these early eras, our blue planet has still not stopped changing. It must be recognized that life on Earth would be impossible without the presence of the atmosphere—the colorless, odorless, invisible layer of gases that surrounds us, giving us air to breathe and protecting us from the Sun's harmful radiation. Although the atmosphere is approximately 435 miles (700 km) thick, it has no clear boundary and fades into space until it finally disappears.
The Earth is known as the blue planet because of the color of the oceans that cover two thirds of its surface. This planet, the third planet from the Sun, is the only one where the right conditions exist to sustain life, something that makes the Earth special. It has liquid water in abundance, a mild temperature, and an atmosphere that protects it from objects that fall from outer space. The atmosphere also filters solar radiation thanks to its ozone layer. Slightly flattened at its poles and wider at its equator, the Earth takes 24 hours to revolve once on its axis.
The Phenomenon of Life
Water, in liquid form, makes it possible for life to exist on the Earth, the only planet where temperatures vary from 32° F to 212° F (0° C to 100° C),
allowing water to exist as a liquid. The Earth’s average distance from the Sun, along with certain other factors, allowed life to develop 3.8 billion years ago.
Magnetism and Gravity
The Earth’s magnetic field originates in the planet’s outer core, where turbulent currents of molten iron generate both electric and magnetic fields. The orientation of the Earth’s magnetism varies over time, causing the magnetic poles to fluctuate.
1.EVAPORATION
Because of the Sun’s energy, the water evaporates, entering the atmosphere from oceans and, to a lesser extent, from lakes, rivers, and other sources on the continent
2.CONDENSATION
The Earth’s winds transport moisture-laden air until weather conditions cause the water vapor to condense into clouds and eventually fall to the
ground as rain or other forms of precipitation.
3.PRECIPITATION
The atmosphere loses water through condensation. Gravity causes rain, snow, and hail. Dew and frost directly alter the state of the surface they cover.
The Earth is known as the blue planet because of the color of the oceans that cover two thirds of its surface. This planet, the third planet from the Sun, is the only one where the right conditions exist to sustain life, something that makes the Earth special. It has liquid water in abundance, a mild temperature, and an atmosphere that protects it from objects that fall from outer space. The atmosphere also filters solar radiation thanks to its ozone layer. Slightly flattened at its poles and wider at its equator, the Earth takes 24 hours to revolve once on its axis.
The Phenomenon of Life
Water, in liquid form, makes it possible for life to exist on the Earth, the only planet where temperatures vary from 32° F to 212° F (0° C to 100° C),
allowing water to exist as a liquid. The Earth’s average distance from the Sun, along with certain other factors, allowed life to develop 3.8 billion years ago.
Magnetism and Gravity
The Earth’s magnetic field originates in the planet’s outer core, where turbulent currents of molten iron generate both electric and magnetic fields. The orientation of the Earth’s magnetism varies over time, causing the magnetic poles to fluctuate.
1.EVAPORATION
Because of the Sun’s energy, the water evaporates, entering the atmosphere from oceans and, to a lesser extent, from lakes, rivers, and other sources on the continent
2.CONDENSATION
The Earth’s winds transport moisture-laden air until weather conditions cause the water vapor to condense into clouds and eventually fall to the
ground as rain or other forms of precipitation.
3.PRECIPITATION
The atmosphere loses water through condensation. Gravity causes rain, snow, and hail. Dew and frost directly alter the state of the surface they cover.
Journey to the Center of the Earth
We live on the Earth, but do we know what we are standing on? The planet is made up of layers of various materials, such as solid and molten rock, which in turn are composed of such elements as iron, nickel, and silicon. Our atmosphere is the layer of gases surrounding our planet. One of these gases, oxygen, does a very special job—it permits life to exist
Internal Structure
We live on a rocky surface similar to a shell. The rocks we live with are made mostly of oxygen and silicon, but underneath them is the mantle, made of much heavier rocks. The mantle also surrounds the inner and outer cores with a region of constantly boiling liquid metals, creating the convective currents that generate the Earth’s magnetic field. The inner core, solid because of the great pressure put upon it, is the densest part of the planet.
Above the Surface
The existence of life on our planet would be impossible without the atmosphere that provides the air we breathe and the water we drink; it also protects us from the Sun’s harmful radiation, while simultaneously maintaining mild temperatures by
retaining the Sun’s warmth. The atmosphere is about
435 miles thick (700 km) but lacks defined limits.The hydrosphere, the liquid part of the Earth,
includes the oceans, lakes, rivers, underground
Hydrosphere and Lithosphere
We live on the Earth, but do we know what we are standing on? The planet is made up of layers of various materials, such as solid and molten rock, which in turn are composed of such elements as iron, nickel, and silicon. Our atmosphere is the layer of gases surrounding our planet. One of these gases, oxygen, does a very special job—it permits life to exist. 71 percent of the Earth’s surface. The lithosphere is a superficial, elastic region that is 4 to 7 miles (6 to 11 km) thick under the oceans and up to 43 miles (70 km) thick under mountain ranges. 3,965 miles (6,380 km)
from the Earth’s surface to its center.
Internal Structure
We live on a rocky surface similar to a shell. The rocks we live with are made mostly of oxygen and silicon, but underneath them is the mantle, made of much heavier rocks. The mantle also surrounds the inner and outer cores with a region of constantly boiling liquid metals, creating the convective currents that generate the Earth’s magnetic field. The inner core, solid because of the great pressure put upon it, is the densest part of the planet.
Above the Surface
The existence of life on our planet would be impossible without the atmosphere that provides the air we breathe and the water we drink; it also protects us from the Sun’s harmful radiation, while simultaneously maintaining mild temperatures by
retaining the Sun’s warmth. The atmosphere is about
435 miles thick (700 km) but lacks defined limits.The hydrosphere, the liquid part of the Earth,
includes the oceans, lakes, rivers, underground
Hydrosphere and Lithosphere
We live on the Earth, but do we know what we are standing on? The planet is made up of layers of various materials, such as solid and molten rock, which in turn are composed of such elements as iron, nickel, and silicon. Our atmosphere is the layer of gases surrounding our planet. One of these gases, oxygen, does a very special job—it permits life to exist. 71 percent of the Earth’s surface. The lithosphere is a superficial, elastic region that is 4 to 7 miles (6 to 11 km) thick under the oceans and up to 43 miles (70 km) thick under mountain ranges. 3,965 miles (6,380 km)
from the Earth’s surface to its center.
Once Upon a Time
The Earth probably formed from material in the solar nebula—the cloud of gas and dust that led to the formation of the Sun. This material gradually grew into a larger and larger body that became a red-hot ball of rock and metal. Later the rocky crust formed, its surface cooling enough to allow the continents to appear. Even later the oceans arrived, as well as the tiny organisms that released oxygen into the atmosphere. Although much of this gas was initially consumed in chemical reactions, over time, it allowed the development of multi cellular organisms and an explosion of life that took place at the start of the Paleozoic Era, 542 million years ago
Continental Drift
We live on the continents, which are part of movable plates that drift across the Earth’s surface at the rate a fingernail grows. 250 million years ago, India, Africa, Australia, and Antarctica were part of the same continent. When tectonic plates rub against each other, land and oceanic crust earthquakes occur. Where the plates separate, a rift forms. The mid-ocean ridges that run beneath the oceans are formed by lava that emerges from the rifts between tectonic plates. Where plates collide, a process called subduction takes place, in which the rocks of the oceanic floor are drawn under the continent and melt, reemerging in the form of volcanoes
1. 290 MILLION YEARS AGO
The super continent called Pangea formed. An immense ocean called Panthalassa surrounded it.
2. 250 MILLION YEARS AGO
The Tethys Sea slowly split Pangea, creating two continents, known as Laurasia and Gondwana.
3.163 MILLION YEARS AGO
Gondwana split, forming Africa and South America as the southern Atlantic Ocean was created.
4.60 MILLION YEARS AGO
The northern Atlantic Ocean slowly separated, completing the formation of Europe and North Africa
Origin of the Earth
The Earth was formed 4.6 billion years ago from a cloud of dust and gas. In the beginning, it was a molten, constantly active, mass. As time passed, the Earth began to cool, and the atmosphere began to clear as rain fell, creating the oceans.
1. 290 MILLION YEARS AGO
The super continent called Pangea formed. An immense ocean called Panthalassa surrounded it.
2. 250 MILLION YEARS AGO
The Tethys Sea slowly split Pangea, creating two continents, known as Laurasia and Gondwana.
3.163 MILLION YEARS AGO
Gondwana split, forming Africa and South America as the southern Atlantic Ocean was created.
4.60 MILLION YEARS AGO
The northern Atlantic Ocean slowly separated, completing the formation of Europe and North Africa
Origin of the Earth
The Earth was formed 4.6 billion years ago from a cloud of dust and gas. In the beginning, it was a molten, constantly active, mass. As time passed, the Earth began to cool, and the atmosphere began to clear as rain fell, creating the oceans.
Romance and terror, mystery and superstition–all these emotions are responses to the Moon, the Earth’s one natural satellite, which always hides one of its two faces. However,whatever symbolic meanings are attributed to the Moon, its gravitational pull has a concrete effect on the Earth—it is a cause of the tides. Depending on the distance of the Moon from the Earth, the gravitational pull exerted by the Moon varies in strength and so can high tides and low tides. To reach full height, tides need large open areas of ocean. For this reason, tides in closed or small bodies of water are much lower.
The Tides
The water on the side of the Earth closest to the Moon feels the Moon’s
gravitational pull most intensely, and vice versa. Two tides are formed, and they track the Moon in its orbit around the Earth. However, they precede the Moon instead of being directly in line with it.
The Lunar Landscape
Observing the Moon, the ancient astronomers decided that, as on the Earth, its plainly visible dark spots must be seas. These dark regions of the Moon contrast against the bright ones, the highlands with the
most impact craters.
The Tides
The water on the side of the Earth closest to the Moon feels the Moon’s
gravitational pull most intensely, and vice versa. Two tides are formed, and they track the Moon in its orbit around the Earth. However, they precede the Moon instead of being directly in line with it.
The Lunar Landscape
Observing the Moon, the ancient astronomers decided that, as on the Earth, its plainly visible dark spots must be seas. These dark regions of the Moon contrast against the bright ones, the highlands with the
most impact craters.