What makes a fossil an index fossil ?

Explanation:

A fossil is an index fossil when it is distinctive, abundant, and limited in geological areas. A good index fossil lived for a short period of time so that the range of ages of the strata in which the index fossil is located is small. A good index fossil is found in a wide geological range.

A fossil is an index fossil when animals or plants preserved in the rock record of the Earth is characteristic by a particular span of geologic time or environment.

ocean expansion, global warming is melting icebergs and causing water levels to rise.

increase soil erosion                                             reduce soil erosion

cattle grazing                                                         hydroseeding

deforestation                                                         contour plowing

                                                                                planting vegetation

plant roots basically hold the top soil

together and stop soil erosion because

in such situation top soil is not removed

during flood but cattle grazing causes

soil erosion because cattle consume the

grasses and herbs and top soil is exposed.

same situation occurs because of

deforestation, the trees and plants are cut

down to expose top soil which causes soil

erosion