The heaviest elements settled in the Earth's center.
The Earth on the other hand starts with a core of iron and radioactive materials such as uranium and plutonium, which release energy in the form of heat, through a process known as nuclear fission. It went through a fusion stage - a "liquid-pasty" state - which allowed that, due to gravity, the denser materials sank towards the center, while the lighter ones floated towards the crust, a process called planetary differentiation.
A hurricane hits a small island,
killing all but a few members of a bird population. This is an example of population
bottleneck effect. The bottleneck effect is a sudden and high reduction of a
population's genetic pool due to environmental actions (such as flood) or human
activities.
Do NOT trust the link from the other user.
It is a Direct contact, droplet infection effects are when the mucosal surfaces of the eyes nose and mouth. Occurs when dental team member inhales aerosol generated by hand piece or air water syringe.