The Earth: The land and the sea

Planet Earth. A globe of green and blue - the land and the sea. Let’s take a closer look at it. Land covers about 30% of the Earth’s surface, forming continents and islands. We commonly talk about six continents: Africa, North America, South America, Antarctica, Eurasia, and Australia.

However, when we talk about regions of the world, Europe and Asia are often described as separate, even though they are connected by land. So there are six physical continents and seven regions of the world; regions are not the same as continents. The land has been shaped by different forces acting on it for millions of years. These forces come both from within the Earth - like volcanic activity or movement of the earth’s crust, and from the outside - like wind, rain, or changes in temperature. These forces create valleys, mountain ranges, or canyons and other landforms!

These different landforms themselves have an effect on weather and climate. Landforms absorb and reflect sunlight in different ways. This creates differences in temperature. Land heats up and cools down faster than water or air. One place where you can easily see this is at the coast!

Because of the varying temperatures between land and ocean, the wind changes direction twice a day. Water covers the remaining 70% of the Earth, and makes our planet look blue! If you look at a map, these blue areas of water have distinct names: the Pacific Ocean - stretching between the Americas in the east and Asia and Australia in the west, the Atlantic Ocean separating Europe and Africa from the Americas, the Indian Ocean, bordered by Asia, Africa and Australia, the Arctic Ocean by the North Pole, and the Southern Ocean surrounding Antarctica. Smaller sections of the ocean, close to the coastal areas, are called seas: for example the Carribean Sea, the Red Sea, and the Mediterranean Sea. In fact, all these oceans and seas are connected to each other and create one large World Ocean.

Just like the land, the bottom of the ocean is made of solid rock. The same landforms on land can also be found underwater. There are underwater mountains, valleys, and much more. However, these underwater landforms are usually much deeper, taller, and wider than those on land. For example, the deepest spot on Earth is within the Mariana Trench in the northern part of the Pacific Ocean.

At a point called Challenger Deep, the depth extends to nearly 11 kilometers straight down below the ocean surface. In comparison - Mount Everest, the highest mountain on Earth is almost 9 kilometers above sea level. If we flipped Mount Everest upside down, its peak would not be anywhere near the deepest point of the Mariana Trench! The land and the sea are home to countless organisms, including us humans! People already know much about the planet Earth, and have been almost everywhere on land.

But there are still places, especially at the bottom of the sea, that are yet to be explored.