Glaciers begin to form when snow remains in the same area year-round, where enough snow accumulates to transform into ice.
Answer:
A physical map
Explanation:
A physical map shows the physical features of an area.
Population density is the study of how many people live in some area as compared to other areas - this helps for example predict whether the area can preduce enough food for itself. It is measured in the number of people per a unit of area.
The correct answer then is:
<span> the number of people who live in a square mile or kilometer</span>
The correct answer is - when an event occurred in years.
The absolute dating tells us exactly when something happened in years. By using the carbon 14 technique it can be very accurate to about 40,000 years ago, and also by studying the rocks, it can be accurate to an incredible 200 million years backwards. This is of great importance for the fields of geology and paleontology, as well as all the sciences that use the information's from them for their own studies. This method allows the scientists to be able to put things into the right order as to when they happened in the geological history, thus creating a very accurate picture of the order of the events that took place in the past of our planet.
Cracks in rocks : mechanical
Lichen growing on rocks : chemical
Roots or plant growth making cracks in the concrete : mechanical
Worn away statues : chemical and mechanical in my opinion
Exposed rocks : mechanical
Rust on rocks : chemical