Tag Archives: Archaean

Slow weather and the world inside

Inside planet Earth is another planet, the size of Mars. Not quite the way Jules Verne or Edgar Rice Burroughs imagined, but …

We live at the boundary between Earth’s solid surface, its liquid water surface, and its atmosphere. The sun pours energy into this boundary, and drives the circulation of water and air. The altitude of the surface varies. Events on this boundary rule our lives. We live at the mercy of weather, worry about climate change and rising sea levels, and (if we are Tibetans or Andean Indians) have genes adapting us to life at high altitude.

There is an equally dramatic landscape 1800 miles deep in the Earth, at the boundary between the oxygen-rich silicate mantle and the iron core. The core-mantle boundary is as dramatic a transition as the Earth-atmosphere boundary. And the boundary is not smooth or featureless: We know, from measuring the choppy irregular pattern of seismic waves that bounce off it, that there is a complex uneven landscape at the boundary. There is a kind of slow weather in the mantle, driven not by the sun, but by heat from the core. The core-mantle boundary has cool uplands where material falling faintly through the viscous mantle from above lays thickly drifted, in mountains hundreds of miles high. It has torrid lowlands, from which hotter, less viscous plumes of magma rise, to generate hotspots far above. (Two of the major plumes nowadays are under the central Pacific and Africa.) And there may also be lakes and seas of liquid silicates at the boundary.

Long-term geological processes – the movement of tectonic plates, the formation and breakup of continents – are driven by this slow weather in the mantle. One theory is that things changed around the end of the Archaean and beginning of the Proterozoic — that the “weather” inside the Earth grew calmer, the lower and upper mantle grew more separate, and the modern pattern of supercontinent formation and breakup began. If this is true, then changes we see at the surface of the Earth, like the rise of an oxygen atmosphere, may owe something to events where mantle meets core.

Slow weather and the world inside

Inside planet Earth is another planet. Not quite the way Jules Verne or Edgar Rice Burroughs imagined, but …

We live at the boundary between Earth’s solid surface, its liquid water surface, and its atmosphere. The sun pours energy into this boundary, and drives the circulation of water and air. The altitude of the surface varies. Events on this boundary rule our lives. We live at the mercy of weather, worry about climate change and rising sea levels, and (if we are Tibetans or Andean Indians) have genes adapting us to life at high altitude.

There is an equally dramatic landscape 1800 miles deep in the Earth, at the boundary between the silicate mantle and the iron core. The core-mantle boundary is as dramatic a transition as the Earth-atmosphere boundary. And the boundary is not smooth or featureless: We know from measuring the speeds of seismic waves that there is a complex uneven landscape at the boundary. There is a kind of slow weather in the mantle, driven not by the sun, but by heat from the core. The core-mantle boundary has cool uplands where material falling slowly through the viscous mantle from above has piled up. It has hot lowlands, from which hotter, less viscous plumes of magma rise, to generate hotspots far above. (Two of the major plumes nowadays are under the central Pacific and Africa.) And there may also be lakes and seas of liquid minerals at the boundary.

Long-term geological processes – the movement of tectonic plates, the formation and breakup of continents – are driven by this slow weather in the mantle. One theory is that things changed around the end of the Archaean and beginning of the Proterozoic — that the “weather” inside the Earth grew calmer, the lower and upper mantle grew more separate, and the modern pattern of supercontinent formation and breakup began. If this is true, then changes we see at the surface of the Earth, like the rise of an oxygen atmosphere, may owe something to events where mantle meets core.

Slow weather and the world inside

Inside planet Earth is another planet. Not quite the way Jules Verne or Edgar Rice Burroughs imagined, but …

We live at the boundary between Earth’s solid surface, its liquid water surface, and its atmosphere. The sun pours energy into this boundary, and drives the circulation of water and air. The altitude of the surface varies. This rules our lives. We live at the mercy of weather, worry about climate change and rising sea levels, and (if we are Tibetans or Andean Indians) have genes adapting us to life at high altitude.

There is an equally dramatic landscape 1800 miles deep in the Earth, at the boundary between the silicate mantle and the iron core. The core mantle boundary is as big a transition as the Earth atmosphere boundary. It is not smooth or featureless: We know from measuring the speeds of seismic waves that there is a complex uneven landscape at the boundary. There is a kind of slow weather in the mantle, driven by heat from the core. The core mantle boundary has cool uplands where material falling slowly through the viscous mantle from above has accumulated. It has hot lowlands, from which hotter, less viscous plumes of magma rise, to generate hotspots above. (Two of the major plumes nowadays are under the central Pacific and Africa.) And there may be lakes and seas of liquid minerals at the boundary.

Long-term geological processes – the movement of tectonic plates, the formation and breakup of continents – are driven by this slow weather in the mantle. One theory is that things changed around the end of the Archaean and beginning of the Proterozoic — that the “weather” inside the Earth grew calmer, the lower and upper mantle grew more separate, and the modern pattern of supercontintent formation and breakup began. If this is true, then changes we see at the surface of the Earth, like the rise of an oxygen atmosphere, may owe something to changes where mantle meets core.

Supercontinents and superglaciers

A week of tweets, from the Archaean Eon to the first great Ice Age

Sunday, February 1. 2.420 – 2.288 Bya

Saturday, January 31. 2.560 – 2.420 Bya

Friday, January 30. 2.708 – 2.560 Bya

Thursday, January 29. 2.864 – 2.708 Bya

Wednesday, January 28. 3.300 – 2.864 Bya

Tuesday, January 27. 3.205 – 3.300 Bya

Monday, January 26. 3.390 – 3.205 Bya

Hadean tweets

Some tweets from the earliest Earth, Hadean and Archean eons

January 25, Sunday. 3.586 – 3.390 Bya (billion years ago)

January 24, Saturday. 3.793 – 3.586 Bya (billion years ago)

January 23, Friday. 4.012 – 3.793 Bya (billion years ago)

January 22, Thursday. 4.244 – 4.012 Bya (billion years ago)

January 21, Wednesday. 4.489 – 4.244 Bya (billion years ago)