During the stages of the Earth formation, ash, lava, carbon dioxide and water vapour discharged onto the surface of the planet by constant volcanic eruption.the water forms the oceans, wile carbon dioxide entered the atmosphere or was dissolved in the ocrans. Cloud,formed of water droplets,reflected some of the sun’radiation back into space. The Earth’s temprature stabilizing and early life forms began to emerge,converting carbon dioxied into life -giving oxygen.
It is taught that the gases that make up the earth’s atmosphere originated deep within the interior , and were realised many milloon of years ago during intense valcanic activity, similar to this eruption at mout st.helens
MILLIONS OF OBJESTS , remnannts of planetry formation, circle the sun in a zone lying between mars and jupiter: the asteroid belt. Fragments of asteriods break of to form meteorides , which can reach the Earth’s surface. Comets,conposed of ice and dust, originated outside our solar system. their elliptical orbit brings them close to sun and into the inner solar systm. Meteor crater in Arizona is 4200 feet (1300m) wide and 660 feet (200m) deep. It was formed over 10,ooo years ago. The orbit of halley’s comet brings it close to the EARTH every 76 years. It’s last visit was on 1986.