Suggest improvements for the highlighted problem area:
The Amazon drains water from a region that is large, tropical and flat. This region is 13 times the size of France but little of the river water comes from mountain snow melt. Most of it's water comes from rain in the vast lowlands. This rain forest, located on the equator experiences the equivalent of two summers each year. The result is two seasonal peaks of rainfall and streamflow. In an area as flat as the Amazon basin, these peaks can cause widespread damage. Floods are common in the city of Manaus, which is 1200 kilometers inland but only 26 meters above sea level.
- Commas in Lists -
The first sentence in our opening paragraph shows an example of punctuation that could be improved:
The Amazon drains water from a region that is large, tropical and flat.
A comma is helpful to separate distinct things in a list:
The Amazon drains water from a region that is large, tropical, and flat.
The best way to list three or more terms in a series that uses a single conjunction is to place a comma between each pair of terms:
mountains, valleys, and lowlands
rain, snow melt, or condensation
Even when each of these terms is a sentence fragment, the same rule applies:
The waters rose, flooded Manaus, and then receded.
There is an exception to this rule. When you are sure that the last two terms in a series are an inseparable pair, you don't need to separate them with a comma:
Awakening on his raft, Dominisio longed for a breakfast of coffee, toast, ham and eggs.