Scientists believe Earth had a twin, Theia. The planets were born in similar orbits and soon collided. A ring of debris left from the obliteration of Theia was orbiting Earth. Earth was impacted by the debris but was absorbed, making Earth a much larger planet. This increased Earth’s gravitational pull, preventing the atmosphere from leaking into space. Our unique atmosphere controls the climate and protects us from UV rays.
The atmosphere has four layers. First there is the warm, unpredictable and oxygen-rich troposphere. It’s 10km thick and contains a rich cocktail of gases essential for life. At about 15km above sea level is the stratosphere where the air is dry. This is where the ozone layer – the barriers that shield us from the sun’s UV rays – lies. At 50km above sea level is the mesosphere. It’s thin, but protects us from meteorites on a trajectory towards Earth. Finally, at 85km above sea level, lies the thermosphere. This is where space shuttles orbit the Earth and where the magnetic field is at work.
Scientists speculate that billions of years ago, Earth was hit by thousands of comets made of rock and ice. When they impacted Earth they transferred their ice to our planet and delivered half of the water that makes up our oceans today. The rest cam from Earth’s molten core. It produced volcanoes that released steam into the atmosphere. When this steam cooled, clouds formed and produced rain. Evidence indicates that the first rainstorm on Earth may have lasted thousands of years.
Why doesn’t Earth get bigger?
The Earth’s surface is broken up into seven plates. They are so enormous that they can carry an entire continent and extend far under the sea. Where the plates collide, one pushes beneath the other. This is known as subduction. The subjected seafloor carries carbon-containing rock down to Earth’s core where it is heated and melted. The build-up of CO2 causes the molten lava to rise to the surface and explode in the form of an eruption. In this way, the old crust at the edge of one plate is replaced by new crust from the edge of another.
If Earth did strike its twin, the massive impact would’ve generated huge amounts of heat and energy. When the surface of these rocks cooled, the heat remained trapped, creating a molten core of energy. It’s the churning of this iron core that gives Earth its magnetic field. Hot rock, melted by the core, rises to the surface and spreads sideways. The Earth’s crust is slowly dragging apart with a new crust forming at the point of eruption.
Land versus water
Where the continents collide, mountain ranges rise up. The higher they are, the higher air needs to travel to pass over them. As the air rises higher and higher; it cools and forms rain-clouds. This rainwater falls onto the top of mountains and runs down them, creating mighty rivers that erode the mountains and carry them to the ocean in the form of sediment.
If it weren’t for the continually moving plates, pushing the ground up and creating mountains, the land would eventually be worn down and washed out to sea, leaving behind a water world.
Three million years ago the collision of North and South America caused the warm Gulf Stream ocean current to move north. The warm waters evaporated, supplying more moisture to the cold northern regions of the planet. The moisture collected in the sky and caused more snow to fall. Slowly, the northern hemisphere iced over. In other words, snow and ice are actually uncommon to Earth and are only presented durning an ice age. Geologists believe we are in the middle of one right now!
In extremely cold places like Siberia, permafrost traps dead plants in the soil. These dead plants ferment and release methane, a gas ten times more harmful to the atmosphere than carbon dioxide. As global temperatures rise, the risk of the permafrost melting increases. If the permafrost completely melted, an enormous amount of methanols would be released into the atmosphere. This, in turn, would speed up global warning, creating a devastating cycle of destruction.
The Human era
Earth is facing its greatest challenge – humankind By burning fossil fuels like coal and gas, we have changed the composition of the atmosphere and, as a result warmed the climate. The rise in temperature is melting permafrost, glaciers and ice sheets, which will cause sea levels to rise that may threaten to flood our cities.
Does this mean that we are destroying our planet? Evolution has shown that over the millennia, Earth has continually evolved, sometimes wiping out entire civilisations and species. A meteorite explosion that is thought to have obliterated the dinosaurs’ 200 million year reign was a mere blip in Earth’s history. Our planet survived only to create life anew in a few million years. Sometimes the resulting species benefited greatly from the previous catastrophe, evolving into ever-complex life forms. So the real question is, is it our planet that needs saving, or is it us?
Check out for more cool articles in vol 4.1!