Answer:
Two possible reasons for the massive extinction at the end of the Paleozoic Era are an asteroid collision and massive volcanic eruptions.
Explanation:
The massive extinction that occurred at the end of the Paleozoic Era is the biggest extinction from what is known so far. The majority of the species died out, and whole families of animals and plants were wiped out of the face of the Earth. It was only small and highly adaptable organisms that managed to survive and give rise to the later life-forms.
The two possible reasons for this massive extinction are an asteroid impact and massive volcanic eruptions. An asteroid collision would have created drastic changes in a matter of minutes and hours, with effects lasting for a long period of time, thus eliminating the majority of the life. Massive volcanic eruptions, with the Siberian super-volcano being the prime candidate, may have caused enormous amounts of carbon dioxide and sulfur dioxide to end up in the atmosphere, thus rapidly changing the living conditions on the planet.
Answer:
Transport of sediments causes them to become rounder as their irregular edges are removed both by abrasion and corrosion. Beach sand becomes highly rounded due to its endless rolling and bouncing in the surf.
Answer:
On their mode of formation
Explanation:
The classification of rocks into three major categories is strictly based on their mode of formation.
Rocks are naturally formed aggregates of minerals. Based on mode of formation, they can be classified into;
- Igneous rocks: these rocks are formed by the cooling and solidification of molten magma.
- Sedimentary rocks are formed by the compaction and lithification of sediment.
- Metamorphic rocks: these are changed rocks that have been formed by subjecting rocks to pressure and temperature conditions which causes an alteration of their minerology.
This movement is called convection. It can be found in liquids, gasses and rheids - solids that can also experience movement ( on a big time scale), such as the earth mantle. One of the types of convection is diffusion: net movement of gasses from higher to lower concentration areas.
