The colon has two major uses:

• to introduce a list (as here)
• to separate two parts of a sentence, where the second part provides more information about or clarifies the first.

Colons should never be followed by a hyphen (-), and the first word that follows the colon is not capitalised except if the word is part of a quote, and is capitalised already. For example:

Marshak is very clear: 'The island owes its existence to a large volcanic hot spot sitting on a mid-oceanic ridge'.

Examples of lists are:

• Three types of Earth scientists were vital to the project: cartographers, seismologists and volcanologists.
  
• There are four main uses for colons: introducing lists; separating two parts of sentence; introducing quotations; and writing ratios.

A colon also leads a reader to expect more detail:

• Mantle plumes leave a trail of extinct volcanoes in their wake: the Hawaiian Islands are a good example.
• To summarise: there are various tectonic settings at which different kinds of volcanism occurs.