How does the earth system change over time?

1 Answer
Mar 22, 2016


It responds to big changes including changes in output from the sun, plate tectonic movements, and random asteroid impacts from space.


The Earth system has been remarkably adept in responding to some of the big changes mentioned above. The conditions for life have also remained very positive for life over the last 3.5 billion years or so. However, this is done by purely physical and biological science processes and not by some Earth Mother or Creator kind of guy or gal!

There are a number of negative feedback loops that act like a thermostat in keeping condition on the planet fairly constant. For example, as the sun's output increases, more heat is bled off into space via the polar regions.

However, for example, massive outputs of volcanic basalts have dumps huge amounts of CO2 in the atmosphere, boosting the natural greenhouse effect and causing a super global warming events. This in turn, sets off feedback loops that make this worse. This happened around 250 million years ago and wiped out nearly 90% of life on the planet. But, life bounced back and survived. Big changes like this usually also change the course of biological evolution.

Periodically in Earth's history, and probably in the future, we get whacked by a giant asteroid and this causes a huge impact on the Earth system - but again, after some thousands or millions of years of recover, the Earth system bounces back! The extinction event at the end of the Cretaceous (65 million years ago) caused the end of the dinosaurs, but evolutionarily , opened up a whole bunch of new niches for mammals and eventually, us humans.