The unevenness of the lay of the land of the Bahama Banks (and the same is true also of the southern portion of Florida, the Yucatan peninsula, and of nearly all of the submarine plateaus or banks in West India waters) is largely due to the maritime life such as the coral reefs and the coral rock formed on these (answer) features. The outer portion of the continental shelf, in most instances, is formed of soft, unconsolidated calcareous mud or ooze. In the tropical seas, the depth and clearness of the water are favorable. As a result, the reef-building coral-polyps become attached and form massive corals.

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.

a: that she is losing interest in her relationship with arobin just took !

you need to do homework when you can make friends : )