The components of the seabed now it's time for aquatic formations.

Lands on Earth

The lands occupy a vast minority on our planet, but for now, we are not threatened by searching in the style of Costner in the “Water World”. Dry surfaces cover an average of 29% of the Earth. They are not evenly distributed:

• Northern hemisphere – 39.4%
• southern hemisphere – 18.7%
• Western hemisphere – 18.6%
• Eastern hemisphere – 36.4%

They are created by six continents: Eurasia, africa, North America, south america, Australia and Antarctica, although sometimes europe and asia are separated – mainly from a cultural or political point of view rather than geology. In addition to the solid continental plates, many islands of volcanic or coral origin protrude above the sea surface. The average height of lands is 875 m.

And the definition of continent : part of the continental block protruding above the sea surface along with the coastal islands that make up the common continental pedestal. The continent must be relatively compact and separated from other intercontinental seas or oceans.

Continental blocks also include continental shelves and slopes, which in practice lie under the water surface.

[rs-ads block=”W środku”]

Lowlands, depression and cryptodepression

The lowest are depressions – these are depressions below sea level but lying on land. There are almost 0.5% of them in the world, mostly in europe – 1.4%. The biggest depression on Earth is the Dead Sea (-418m above sea level), and in Poland Żuławy Wiślane (-1.8 m above sea level). Other known depressions are Death Valley in the USA (-86 m above sea level), the Caspian Lowland (-28 m above sea level), Lake Eyre in Australia (-15 m above sea level).

If we fill such depression with water or ice so that the bottom is below sea level and the water table is most often above we will receive crypto depression. Water crypto depression includes Lake Baikal (1164 m deep), Caspian Sea (1053 m) and Dead Sea (735 m), Lake Tanganyika (698 m) and Lake Ladoga (230 m). Fans of horror stories also have their crypto depression – Scottish Loch Ness. In Poland, the largest crypto depression is Lake Miedwie near Szczecin (30 m).

Ice crypto depressions are less known, so let's remember even the deepest – the Bentley ditch (-2496 m a.s.l.) and the depression under the Byrd Glacier (-2870 m a.s.l.).

Further, forms of relief will be above sea level. Lowlands rise from 0 to 300 m a.s.l. They occupy 33.5% of the planet's surface, most of them occur in Europe, where they occur in 72.6% of our continent.

We divide the lowlands into:

• coastal – located on the banks, their extension is the continental shelf
• flat – resulting from the deposition of river sediments and some post-glacial sediments
• wavy with a height difference of up to 30 m – former flat lowlands, but subjected to wind and water erosion
• hilly with a height difference of up to 60 m – arise as a result of severe erosion and accumulation (wind and water), sedimentation (glacial and river), most often on the foreland of glaciers.

[rs-ads block=”W środku”]

Highlands and mountains

The lower limit of the highlands is considered 300 m a.s.l., the upper reaches up to 5000 m a.s.l. in the case of the Tibetan Plateau. Highlands often go to the mountains, so it is not advisable to suggest heights. What makes them stand out is the slightly hilly terrain or the flat landscape when the levelling surface is high.

The most fascinating are mountains. They have varied terrain, high relative heights and steep slopes. The highest mountain is Mount Everest / Czomolungma (8848/8850 m a.s.l.)

Mountains can be:

• individual peaks e.g. Kilimanjaro
• mountain ranges – a group of mountains arranged in lines sharing a common ridge
• mountain chain – several parallel mountain ranges with valleys between them, e.g. Cordillera, Andes, Pyrenees, Alps, Himalayas
• mountain systems – set of mountain ranges from the same period

In addition, the mountains are divided by origin:

• fold mountains – piled up folds and mantles, mostly in a continuous form
• fault blocks – lithosphere blocks shifted along faults
• dome mountains – created as a result of pushing up a fragment of the lithosphere by lacolite without breaking the rock continuity
• volcanic mountains – the result of a volcanic eruption

This post is also available in: polski