Earth continues to evolve.  So far it has taken, notwithstanding Bishop Ussher’s different view of things, about 4.6 billion years for the atmosphere, hydrosphere, lithosphere (the solid earth), and biosphere to get to where they are today.  Over that time there have been (rewording a well-known expression) long geological periods of inexorably slow change punctuated by catastrophes.  Mass extinctions, caused by blink-of-an-eye bolides and episodes of rampant volcanism (e.g. the Deccan Traps), completely changed the course of biological evolution.  Contrast events like these with the life and death of oceans counted over 100-200 million years.  Meteorites, volcanoes, and glaciations have all played their part in moulding our planet. Continue reading →