Final answer:
The term 'NOA' does not refer to an explosive eruption type, making it the correct answer among the given options. Plinian, Strombolian, and Phreatomagmatic eruptions are all explosive in nature, whereas Hawaiian eruptions are less explosive.
Step-by-step explanation:
The question asks which of the following is not an explosive eruption type:
- Plinian
- Hawaiian
- Strombolian
- Phreatomagmatic
- NOA
In the context of volcanic eruptions, 'NOA' does not refer to an eruption type and is therefore the correct answer. The other options listed - Plinian, Strombolian, and Phreatomagmatic - are all types of explosive volcanic eruptions, each with distinct characteristics. For example, Plinian eruptions are marked by their explosive force and the ejection of large amounts of pumice and ash. In contrast, Hawaiian eruptions are typically less explosive and are characterized by effusive lava flows.