Classify the events as autogenic or allogenic succession.

a volcanic eruption
wiping out an
entire island

a soybean crop
in nitrogen fixation, leading
to the development of
other species

a tsunami devastating
all the living organism
in a habitat

oak trees preventing
the growth of smaller
sun-seeking shrubs

In ecology, allogenic succession is mediated by the abiotic components of the ecosystem, while the autogenic succession refers to the succession, which is mediated by the biotic components of an ecosystem.  

A volcanic eruption wiping out an entire island is an example of allogenic succession.  

A soybean crop helping in nitrogen fixation, leading to the development of other species is an illustration of autogenic succession.  

A tsunami devastating all the living organism in a habitat is an example of allogenic succession.  

Oak trees preventing the growth of smaller sun-seeking shrubs is an example of autogenic succession.  

weathering is the answer.