Big Ideas in Volcanology #08:


#08.4 _ Other external sources had a significant role in the formation of the current hydrosphere

The amount of water on Earth can never have been produced by volcanism and degassing alone. It is assumed that water was derived from impacting comets that contained ice, and additional water was imported by bolide collisions, probably from asteroids ejected from the outer asteroid belt under the influence of Jupiter's gravity. These events have been defined by Albarède (2009) as “late veneer”. Computer simulations show that comets were originally far more common in the inner parts of the solar system although most comets are today in orbits farther away from the Sun. However, most of the water on Earth was probably derived from small impacting protoplanets, objects comparable with today's small icy moons of the outer planets. Impacts of these objects could have enriched the terrestrial planets (i.e. the Earth, Mars, Venus and Mercury) with H2O, CO2, CH4, N2 and other volatiles. Conversely, if all water on Earth was derived from comets alone, millions of comet impacts would be required to support this theory and computer simulations illustrate that this is not an unreasonable number.

A tentative chronology of the Earth’s accretion (Albarède, 2009)


Earth’s hydrosphere comes from Volcanic Degassing

#08.1                    #08.2                    #08.3                    #08.4                    #08.5                    #08.6