Earth-Bound: What Do We Need To Know About Our Home Planet

Earth, as we know it, is our home and the third planet from the distant and biggest star in the solar system. It hosts different living things in so many shapes and sizes. But how much exactly do we know about this special place in the universe, and how important is it to our study and understanding of weather?

The Earth is smaller than the planetary “giants”Jupiter, Saturn, Uranus, and Neptune but larger than the three other rocky planets Mercury, Mars, and Venus. As we scale up and down, we will find our planet has a diameter of roughly 13,000 kilometers and is approximately round by appearance, all thanks to its gravitational pull. Its “spin” is deliberately held at its poles, (North and South) while it appears swollen with a signature ‘’bulge’’ along the equator.

Our planet has something very crucial in terms of survival that others do not have – water. Water plays a central role in our weather, and it is fundamental to and interrelated with almost everything that has life on Earth.

Layers of the Earth

The Earth is a multi-structural system composed of various sections. These are core, mantle, and crust. The three divisions are based on their composition. For one, the crust’s make-up is about less than 1%, consisting of oceanic and continental crust, which are often more felsic (rich in feldspar and quartz) rock. The mantle, on the other hand, is hot and represents about 68% of the Earth’s mass. Finally, the core is mostly made up of iron metal. The core is about 31% of the Earth. 

Crust and Lithosphere

The Earth’s outer surface is its crust and lithosphere: a cold, thin, brittle outer shell made of rock. The crust is very thin, relative to the radius of the planet which is around 6,371 kilometers. There are two different types of crust, each with its own distinctive physical and chemical properties: oceanic and continental.

Oceanic crust is composed of magma that erupts on the seafloor to create basalt lava flows, or cools deeper down to create the intrusive igneous rock called gabbro. Sediments, primarily mud and the shells of tiny sea creatures, coat the seafloor.

Continental crust is made up of many different types of igneous, metamorphic, and sedimentary rocks. The average composition is granite, which is less dense than the mafic (rich in magnesium and iron) igneous rocks of the ocean crust. The crust lithosphere is the Earth’s outermost mechanical layer, which behaves as a brittle and rigid solid. The lithosphere is about 100 kilometers thick.  


The two most important things about the mantle are: (1) it is made of solid rock, and (2) it is hot. Scientists know that the mantle is made of rock based on evidence from seismic waves, heat flow, and meteorites. The properties fit the ultramafic rock peridotite, which is made of iron – and magnesium-rich silicate materials. Peridotite is rarely found on the Earth’s surface. Meanwhile, scientists know that the mantle is extremely hot because of the heat flowing outward from it and because of its physical properties.


At the planet’s center lies a dense metallic core. Scientists know that the core is metal for a few reasons. The density of the Earth’s surface layers is less than the overall density of the planet, as calculated from the planet’s rotation. Calculations indicate that the core is about 85% iron metal, with nickel-metal making up much of the remaining 15%. Also, metallic meteorites are thought to be representative of the core. If the Earth’s core were not metal, the planet would not have a magnetic field.

It is important to explore and acquire basic knowledge about the planet Earth. The more we understand about it, the better we are able to prepare for the different possible phenomena that we can experience in the environment surrounding us. After all, the ground we stand on and the air we breathe (ad\nd everything that happens in between) are connected. As we have always said in the past, it is always best to be prepared. Stay #WeatherWiser!

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–By Adonis S. Manzan

Typhoon Specialist, WeatherPhilippines Foundation, Inc.

7 November 2019




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