The ocean floor is composed of oceanic plates. Interactions with water, plate tectonics and CO₂. The presence of liquid water and plate tectonics are thus intimately linked. Over long timescales, plate tectonics helps maintain Earth’s surface temperature in the range that allows surface waters to be liquid. This delivery is sustained through plate tectonics. Without tectonics, no oceans without oceans, no tectonicsĪlthough carbon sinks store CO 2 away from the atmosphere, volcanoes and oceanic ridges deliver CO 2 back into the atmosphere.

There, the organic matter is incorporated into sedimentary rocks, where it can be stored for millions of years. Organisms on land and in the ocean use CO 2 to build organic matter during photosynthesis, a portion of which is deposited at the bottom of the ocean when the organisms die. The second sink is organic carbon stored in sedimentary rocks.

Calcium combines with the dissolved CO 2 to form carbonate rocks such as limestone, one of the main carbon sinks. First, the acidifying effect of CO 2 dissolved in surface waters causes rocks to dissolve, which releases calcium. The greenhouse effect decreased over time because CO 2 can be removed from the atmosphere by two processes. However, levels of greenhouse gases such as CO 2 and methane were much higher than today, which maintained surface temperatures high enough for water to be liquid. Interactions between sunlight, albedo, and greenhouse gases have maintained a fairly constant energy balance since the first oceans appeared on Earth.Įarly in the Earth’s history, the young Sun was less bright and our planet received less energy from it. Without greenhouse gases, Earth’s surface would be at a temperature around -15☌ and probably devoid of liquid water. Greenhouse gases, which trap solar radiation within Earth’s atmosphere. The albedo of the surface, meaning how much it reflects solar radiation away. The average temperature on a planet’s surface depends on the interaction of three parameters that can vary widely from one planet to the next: Earth’s surface is thus kept within a temperature range that might seem large to us, but is actually fairly narrow when compared with other planets, and it has remained so for billions of years. On Earth, at sea level, water freezes below 0☌ and boils at 100☌. Today, Earth’s average surface temperature is about 15☌, colder than Venus (465 ☌) and warmer than Mars (-60 ☌ on average). This incredible characteristic is due to the interactions of the water cycle with plate tectonics and the greenhouse effect, as well as the configuration of the solar system. If the Earth was first red and black, it has been blue for more than 4 billion years, with rare exceptions when it got too cold and turned into a white snowball. Earth sciences allow us to explain why the Earth has almost always been blue: it’s neither too warm nor too cold. There is only one known planet with permanent bodies of liquid water at its surface: ours. How has the Earth managed to sustain liquid water on its surface for such a long time? The Earth has been blue for over 4 billion years because of the liquid water on its surface.

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