The earth - class-IX

A globe is a miniature form of the earth, which represents distances, directions, continents, oceans, countries, etc. A globe is often misconstrued with a map, which diagrammatically represents the earth's surface or a part thereof, based on scale.

The Earth's core is primarily composed of nickel (Ni) and iron (Fe), which is why it is referred to as Nife. Sial and Sima refer to layers of the crust.

Convergent plate boundaries are known as destructive boundaries because tectonic plates collide, leading to the subduction or destruction of lithospheric material.

The habitable portion of the Earth's land area is significantly less than half, as much of the land is covered by deserts, mountains, ice caps, or dense forests that are not suitable for large-scale human habitation.

• The surface of the earth is still irregular in spite of millions of years of gradation, because— material re-elevates the land. Parts of the crust have been uplifted.
  
• Delamination of the lithosphere has two major geologic effects. First, because a large portion of dense material is removed, the remaining portion of the crust and lithosphere undergo rapid uplift to form mountain ranges. 
  
• Second, the flow of hot mantle material encounters the base of the thin lithosphere and often results in melting and a new phase of volcanism.
  
• Delamination may thus account for some volcanic regions that have been attributed to mantle plumes in the past.

• The shape of the Earth is classified as an ellipsoid or an oblate spheroid.
• The Earth is not considered a true sphere because it has a larger circumference and diameter at the equator.
• The poles of the Earth are squished, which creates a slight bulge around the equator.
• The Earth's polar diameter is about 43 kilometers shorter than its equatorial diameter, a difference of about 0.3%.
• This is due to the equatorial bulge caused by the Earth's rotation.

• The latitudinal extent influences the duration of the day and night as one moves from south to north.
  
• The length of day and night depends on whether the place is receiving direct sun rays or slanting rays.
  
• Places on the equator receive the direct rays of the sun all year round and hence have equal days and night.
• Whereas for places north and south equator, the duration varies according to seasons due to the tilt of the earth.

• The distinguishing features of Earth: abundant liquid water (and the temperature required for that), a protective atmosphere, a geological system neither overactive nor dead.
  
• Earth gravitationally interacts with other objects in space, especially the Sun and the moon.
  

• The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly.
  
•  The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets  being primarily composed of rock and metal.
  
•  The four outer planets are giant planets, being substantially more massive than  than the terrestrials.
  
•  For most of history, humanity did not recognize or understand the concept of  the Solar System. 
  

• The total surface area of the earth is 510 million square km approximately or 510,100,500 square km. Hence option A is correct 

• The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks.

• Earth began to form over 4.6 billion years ago, from the same cloud of gas (mostly hydrogen and helium) and interstellar dust that formed our Sun, the rest of the solar system and even our galaxy.

• The outer core of the Earth is a fluid layer about 2,300 km (1,400 mi) thick and composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle.

• The core is 2900-6376 kms in thickness.
  
• It is composed of dense and heavy substances like iron and nickel.

The crust is the outermost solid shell of the Earth where human beings and other life forms reside.

The mantle is the layer of the Earth located between the crust and the core, extending from a depth of approximately 100 km to 2900 km.

• So, even though it is hotter in the inner core, the pressure in the core is also higher, and you can have solid iron-nickel instead of liquid.
  
• It is made of iron and nickel. 
  
• This is above the Earth's solid inner core and below the mantle. Its outer boundary is 2,890 km (1,800 mi) beneath the Earth's surface..
  
• Convection of liquid metals in the outer core creates the Earth's magnetic field.
  

• Planet Earth has been called the "Blue Planet" due to the abundant water on its surface. 
• Here on Earth, we take liquid water for granted; after all, our bodies are mostly made of water.
• However, liquid water is a rare commodity in our solar system.

• Planet Earth has been called the 'Blue Planet' due to the abundant water on its surface.

• Of the eight planets in the solar system, the fifth-largest planet is Earth.

• Asia is the largest and Australia is the smallest continent.

Large and continues land masses on surface of the earth are termed as continents. This division on the earth as continents are done by us. Our planet is divided into seven large continental masses, these are, Asia, Europe, Africa, North America, South America, Australia and Antarcatica. Among them Asia is the largest and Australia is the smallest continent.

In carboniferous period all the land masses were united together in the form of one land mass which was named as Pangaea. There were several smaller inland seas  scattered over Pangaea which was surrounded by a huge water body named as Panthalasa representing Pacific Ocean. Luratia consisting of present North America, Europe and Asia formed norther part of Pangaea while Gondwanaland consisting of South America, Africa, Madagascar, Peninsular India, Australia and Antarctica represented the southern part of Pangaea. South pole was located near present Durban.

The shape of the earth seems like a sphere, although it is not perfectly spherical. It is rather an oblate spheroid because of the earth's diurnal rotation, i.e, the earth is slightly flattened at its polar ends and bulged out at the equatorial part.

Convection current theory of Holmes dealt with the continental drift, which led to the formation of continents as we see them today.

The formation of a rainbow involves a series of physical phenomena- reflection, refraction, dispersion and total internal reflection. The occurrence of each of these is due to the interaction of light with air and water and the boundaries between them.

Escape velocity is the minimum speed needed for an object to escape from a massive body, in the sense of becoming neither on the surface nor in closed orbit of any radius no matter how great, without the aid of thrust, or suffering the resistance from friction. The escape velocity from Earth is about $11.186$ km/s$(6.951$ mi/s; $40,270$ km/h; $25,020$ mph$)$ at the surface.

A natural satellite is any celestial body in space that orbits around a larger body. Moons are called natural satellites because they orbit planets.  

Satellites that are made by people and launched into orbit using rockets are called artificial satellites. There are thousands of artificial satellites orbiting the Earth.

The inner planets, Mercury and Venus have no natural satellites; Earth has one large natural satellite, known as the Moon; and Mars has two tiny natural satellites, Phobos and Deimos.

Other outer planets also have many natural satellites.

This airplane taking off from N30 E50 would have to be a seaplane or floatplane. That location is in the Persian Gulf off the coast of Iran. 

The oblate spheroid, or oblate ellipsoid, is an ellipsoid of revolution obtained by rotating an ellipse about its shorter axis. It is the regular geometric shape that most nearly approximates the shape of the Earth. A spheroid describing the figure of the Earth or other celestial body is called a reference ellipsoid.

The Suakin Trough, located off the coast of Port Sudan, is known as the deepest part of the Red Sea.

The equator represents the 0° latitude. It divides the earth into two hemispheres: Northern Hemisphere and Southern Hemisphere. All the parallels north of the equator are called "North latitudes" and all parallels south of the equator are called "South latitudes".

A lunar eclipse occurs when the Moon passes directly behind the Earth into its umbra (shadow). This can occur only when the sun, Earth and moon are aligned (in "syzygy") exactly, or very closely so, with the Earth in the middle. 

• The largest planet in our solar system by far is Jupiter, which beats out all the other planets in both mass and volume. Jupiter's mass is more than 300 times that of Earth, and its diameter, at 140,000 km, is about 11 times Earth's diameter.
  

• The shape of the earth is like an oblate spheroid i.e. a sphere which is a little flatter at the pole. Hence option D is correct. 
• The shape of the earth is also called the geoid shape.

The Earth's magnetosphere extends significantly into space, and 64,000 km is a commonly cited figure for the extent of the magnetic belt.

The Moon is a natural satellite that orbits the Earth.

A continuous mass of land in the surface of the earth is termed as continent. There are 7 continents in our surface of the earth namely, Asia, Africa, North America, South America, Europe, Australia and Antarctica. Asia is the largest continent and Australia is the smallest continents in the surface of the earth.

An Astronomical Unit (AU) is defined as the average distance between the Earth and the Sun, approximately 150 million kilometers.

The average distance between the Earth and the Moon is approximately 238,855 miles, which aligns with the provided option.