Laurette Piani has received resources from the nationwide Research firm for her work on meteorite water.

You are watching: Why earth is called blue planet

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Seen from space, the planet is blue. The earth has been blue because that over 4 exchange rate years because of the liquid water on its surface. How has actually the Earth managed to sustain fluid water top top its surface ar for together a lengthy time?

There is just one known planet with long-term bodies of fluid water in ~ its surface: ours. Earth sciences allow us to explain why the planet has practically always to be blue: it’s no too heat nor too cold. If the earth was first red and black, it has actually been blue for more than 4 billion years, v rare exceptions once it gained too cold and turned right into a white snowball.

This incredible characteristic is because of the interaction of the water cycle through plate tectonics and the greenhouse effect, and also the construction of the solar system. Today, Earth’s median surface temperature is around 15°C, colder than Venus (465 °C) and also warmer than Mars (-60 °C top top average). On Earth, in ~ sea level, water freezes listed below 0°C and boils in ~ 100°C. Earth’s surface ar is hence kept within a temperature selection that could seem huge to us, but is actually reasonably narrow when compared with various other planets, and it has actually remained so for billions of years.

Greenhouse gases play their part

The median temperature top top a planet’s surface relies on the interaction of three parameters that have the right to vary commonly from one planet to the next:

The energy showing up from the Sun.

Interactions in between sunlight, albedo, and greenhouse gases have maintained a fairly continuous energy balance due to the fact that the first oceans appeared on Earth.

Early in the earth history, the young sun was much less bright and also our planet received less power from it. However, levels of greenhouse gases such as CO2 and also methane to be much higher than today, which kept surface temperature high enough for water to be liquid.

The greenhouse effect reduced over time because CO2 deserve to be gotten rid of from the environment by two processes. First, the acidifying result of CO2 dissolved in surface waters reasons rocks to dissolve, i m sorry releases calcium. Calcium combines with the liquified CO2 to type carbonate rocks such as limestone, one of the key carbon sinks.

The second sink is essential carbon save in sedimentary rocks. Biology on land and in the s use CO2 to build organic matter throughout photosynthesis, a part of i beg your pardon is deposit at the bottom the the s when the organisms die. There, the organic matter is incorporated into sedimentary rocks, wherein it deserve to be save for millions of years.

Without tectonics, no oceans; there is no oceans, no tectonics

Although carbon sinks store CO2 far from the atmosphere, volcanoes and oceanic ridges supply CO2 earlier into the atmosphere. This delivery is sustained through plate tectonics. Over lengthy timescales, bowl tectonics helps maintain Earth’s surface temperature in the selection that enables surface waters to it is in liquid. The visibility of fluid water and also plate tectonics are thus intimately linked. Just how does the happen?

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Interactions v water, plate tectonics and also CO₂. Guillaume Paris, Author noted

The ocean floor is created of oceanic plates. They relocate away indigenous oceanic ridges, the chain the submarine volcanoes the runs throughout the planet, and then down toward the depth of the earth through subduction. During the thousands of millions that years the they traverse the oceans, oceanic plates become hydrated: your minerals combine water, which modifies your mechanical properties. Together they space subducted, oceanic plates ultimately dehydrate; the released water ultimately produces magmas that type granites, the radical of the continents. Without fluid water, there would be no tectonics and also therefore, no continents!

Due come this recycling of enlarge oceanic plates into the mantle, brand-new plates space constantly being formed from material erupted at oceanic ridges. As this material rises through the mantle and also to the s floor, it cools and releases CO2, helping sustain greenhouse gas concentrations. Water stays liquid and the earth remains blue, together it has been for several billion years.

From black and red to blue

A trace of the oldest oceans: pillow lavas that are 3.8 billion year old (Greenland). Guillaume Caro, Author provided

It has long been assumed the water-rich celestial body from the external solar system brought water come the recently formed Earth. Among our team freshly published a research that questions this hypothesis and suggests that water – the is, hydrogen and oxygen – might have been lugged instead by the rocks that created the Earth.

When the Earth an initial formed 4.5 billion year ago, the was probably too warm for water come be liquid at the surface. In any type of case, if there had actually been oceans, lock would absolutely have vaporized top top the giant affect between the young Earth and a planetary body (probably as huge as Mars), i m sorry melted the surface ar of our planet and also formed the Moon 4.4 billion years ago.

As the earth surface slowly cooled and solidified after ~ the impact, the was most likely covered in dark basaltic rocks, with neither life no one water. Cooling magmas release facets such as hydrogen, oxygen, and also carbon as gas containing molecule such as water, carbon dioxide, and/or methane. The an initial oceans may because of this have formed reasonably quickly after ~ the impact. The an initial known minerals on planet bear the chemical signature of interactions through liquid water. Thus, earth may have actually been blue for almost 4.4 billion years.

The very first indisputable evidence of seas on Earth’s surface is 3.8 billion years old, consisting of the oldest naval sediments, discovered in Isua and also Akilia (Greenland) and Nuvvuagittuq (Canada), and the oldest pillow lavas, uniquely shame rocks that type as lava cools underwater.

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modern-day pillow lavas creating underwater near Hawaii. NOAA

Whether 3.8 or 4.4 billion years old, the history of the seas is attached to that of the Earth and life. Today, human activities are bring about the oceans to become more acidic and also warmer. Oceans won’t disappear, yet the life in ~ is endangered. Our CO2 emissions exceed global volcanic emissions by a variable of 70, endangering the currently balance between processes operation at the earth surface and also those deep within it. Our societies depend on both.