Last time we saw about a cross section of the earth, the solar system, size of galaxies and the universe. But now let’s have a croser look of our planet earth and compare her with her near neighbouring planets in the solar systems.
Let’s start with the age of our planet earth.

Unfortunately, the age cannot be computed directly from material that is solely from the Earth. There is evidence that energy from the Earth’s accumulation caused the surface to be molten. Further, the processes of erosion and crustal recycling have apparently destroyed all of the earliest surface.

The oldest rocks which have been found so far (on the Earth) date to about 3.8 to 3.9 billion years ago (by use of several radiometric dating methods).

Some of these rocks are sedimentary, and include minerals which are themselves as old as 4.1 to 4.2 billion years. Rocks of this age are relatively rare, however rocks that are at least 3.5 billion years in age have been found on North America, Greenland, Australia, Africa, and Asia.

While these values do not compute an age for the Earth, they do establish a lower limit (the Earth must be at least as old as any formation on it). This lower limit is at least concordant with the independently derived figure of 4.55 billion years for the Earth’s actual age.

What is the size of the planet earth?

The total area of the Earth is approximately 510 million square kilometres and the oceans cover about 71 percent of the Earth’s surface, which is about 360 million square kilometres. The diameter of earth is 12,756.3 kilometres.
How does the earth look like from the moon?

One side of the moon always faces us. So you’d have to be on that near side of the moon to see Earth at all. Also, Earth and the moon are both worlds in space, and they’re always half illuminated by the sun. Both have a "day” side and a "night” side. That’s why we see phases of the moon.
When you see a crescent moon, for example, you’re seeing a slim fraction of the moon’s day side while its night side might or might not be visible against the blackness of space.

Now let’s look at the hottest and coldest points on earth.
Hottest Place on Earth

Death Valley is famously blistering hot, but the hottest place ever officially recorded to outdo Death Valley’s amazing heat is El Azizia in Libya. In 1922 the temperature reached 136 degrees. Death Valley’s hottest temperature on record is 134 degrees. When it’s that hot, what’s another two degrees really?

Coldest Place on Earth

Antarctica is a land of extremes. It’s not inhabited year round by humans because it’s simply too freezing cold. In 1983 scientists recorded extremely cold temperatures, as low as -129 Fahrenheit. It’s also the wettest place on earth, but simultaneously the driest. The reason it’s the "wettest” is not because of rainfall; since Antarctica is covered by 98% ice, it’s technically very wet.

However since it’s also the aforementioned coldest place in the world, it gets very little precipitation - less than 2 inches a year. Which makes Antarctica a desert? A brutally cold ice desert with a massive trench full of even more…ice. Three for the price of one!
Records

On September 13, 1922 a temperature of 57.7°C (135.9°F) was recorded in the city of Al ‘Aziziyah, Libya the hottest recorded temperature ever on the surface of the Earth.
On July 21, 1983, the lowest temperature ever recorded on earth was in Russian Vostok Base, Australian Antarctic Territory with −89.2 °C (−128.56 °F).

What is the use of locating seismic discontinuities?
Locating these disturbances enables scientists to map the inner regions of the Earth. This science, known as tomography originates from the knowledge gained from discontinuities.

Tomographists have found that this planet is divided into six regions: the inner core, the outer core, the lower mantle, the upper mantle, the transition region, and the crust (oceanic and continental).

Here is a brief synopsis of the depths of each layer  (in kilometres):

1.0- 40 Crust
2.40- 400 Upper mantle
3. 400- 650 Transition region 4. 650-2700 Lower mantle
5. 2700-2890 D’’ layer
6. 2890-5150 Outer core
7. 5150-6378 Inner core

The inner core is a solid section of the Earth and is unattached to the mantle being suspended by the molten outer core. This solidified state is the result of a very intense pressure-freezing process that occurs in most liquids when temperature decreases or pressure increases.

The outer core of Earth is a scorching hot electrically conductive liquid in which convection takes place.

This inner layer in mutual combination with the rotational motion of the Earth creates a dynamo effect where a force field of electrical currents is generated.

This field is also known as Earth’s magnetic field which is responsible for the functioning of mechanical and biological compasses.

This field also causes a subtle jerking motion in the Earth’s daily rotation. In terms of the physical aspects of the outer core the layer is dense but not as dense as pure molten iron evidencing the presence of multiple impurities having a lighter chemical makeup.

According to scientists, about 10% of this layer is composed of sulfur and/or oxygen due to the fact that these two elements are abundant in the cosmos and dissolve readily in molten iron.

1.The outer core is in the range of 200 to 300 kilometres (125 to 188 miles) thick and represents about 4% of the mantle-crust mass. This layer is sometimes identified as part of the lower mantle due to its geographical nature. However, studies on seismic discontinuities suggest that this "D” layer might differ chemically from the lower mantle lying above it.

2.Looking at the lower mantle, its chemical composition includes silicon, magnesium, and oxygen. Most likely, it probably also contains some iron, calcium, and aluminium. This layer is comprised of 72.9% of the antle-crust mass, making the Earth abundant in the chemical elements of silicon, magnesium and oxygen, the layer’s primary components.

3. Higher up, we encounter the upper mantle. Through excavations in volcanoes, scientists have found that this part of the crust composes of 15.3% of the total mantle-crust mass and is made of crystalline forms of Olivine (Mg,Fe)2SiO4 and pyroxene (Mg,Fe)SiO3.

The upper mantle makes up 10.3% of the Earth’s mass, extending a depth of 6-250 miles (10-400 kilometres). A relatively large portion when compared to the other interior layers. This layer is not completely made of solid minerals for scientists speculate that the asthenosphere could be partly liquid molten.

4. D: The D” layer of Earth is about 3% of Earth’s mass is 125 to 188 miles (200 to 300 kilometres) thick and covers about 4% of the mantle-crust mass.

This layer, in terms of whether it is part of the lower mantle or an independent layer is still somewhat unclear. Based on evidence collected from seismic discontinuities, the D” layer might differ in chemical composition from the lower mantle above it.

5. The next layer, the Transition region comprises 7.5% of Earth’s mass with a depth of 250-406 miles deep (400-650 kilometres). This layer is also known as the mesosphere and is 11.1% of the mantle-crust.

It is made of mainly basaltic magmas with amounts of calcium, aluminum and garnet (an aluminum-bearing silicate mineral). The layer becomes dense when the garnet mineral cools but is buoyant and light when subject to heat due to the low melting points.

6. The outer most layer, the crust, is categorized into two parts, the Oceanic crust and the continental crust. The Oceanic crust is the smallest part of Earth, only 0.099% of its mass and reaching a small depth of 0-6 miles (0-10 kilometers).

In the beginning of time, it was possible that this area did not exist for through frequent volcanic activity does only the crust form. Evidence of this is marked by the oceanic ridge system, which is a 25,000 mile (40,000-kilometer) arraché of many volcanoes which creates layer after layer of new crust at the rate of 17 km3 per year.

The ocean floor is covered in basalt originating from volcanic activity and as a matter of fact, Iceland and Hawaii are two island systems that emerged from the accumulated basalt.

8.Continental crust: The second smallest area of the Earth is the Continental crust, making up only 0.374% of the Earth’s mass and extending a short depth of 0 - 31 miles (0-50 kilometres). Looking at the percent by composition, the continental crust makes up only 0.554% of the mantle-crust mass.

The layer is composed primarily of crystalline rocks made of low-density buoyant minerals dominated mostly by quartz (SiO2) and fieldspars (metal-poor silicates). This is the outer part of the Earth composed essentially of crystalline rocks.

The continental crust and the oceanic crust are also referred to as the lithosphere because of the cool and rocky conditions that exist in its chemical composition.

‘To be continued’

Email : calebnda1@yahoo.com