This infobox is meant to be used on pages about volcanic eruptions and on the sections of articles about a volcano about an eruption, but not as the main template on the pages of the volcanoes themselves (for that, use {{Infobox mountain}}). The completely expanded form of the template is as follows:

{{Infobox eruption
 | name =
 | image =
 | image_size =
 | caption =
 | date =
 | time =
 | volcano =
 | type =
 | location =
 | coordinates =
 | VEI =
 | map =
 | map_size=
 | map_caption =
 | impact =
}}
Field name Input
name Name of the eruption. The conventions for naming relatively modern eruptions is to use "[Year] eruption of [volcano]". See for instance 1980 eruption of Mount St. Helens. If the timing is incomplete (common for extremely old eruptions), use as specific a time period as you may in place of the year. Many eruptions have names given to them by the scientific community, if one exists, use it!
image Photo of the eruption. A painting or other representation may be used for eruptions preceding the invention of photography. Precede filename with "File:" but do not use [ ] brackets.
image_size Size of the photo; leaving this blank will cause it to default to 250px.
caption Caption for the photo.
date Date of eruption; should be as specific as allowable.
time Time of initial eruption; should be as specific as allowable.
volcano Name of the volcano where the eruption occurred.
type Type of eruption, see Types of volcanic eruptions for the different types.
location Location of the volcano, e.g. "Boulder Springs, Colorado"
coordinates Coordinates of the volcano. Use Template:Coord.
VEI Volcanic Explosivity Index, a measure of an eruption's strength similar to the Richter scale; the type of eruption can be inferred off its VEI, and this field also automatically adds the volcano to the respective "VEI-level volcanoes" category.
map Map of the eruption, if there is one. You can use a {{Location map}} template in place of a "hard" image map (use width = 250, with caption = )
map_size Same as image_size, above.
map_caption Caption for the map.
impact What was the impact of the eruption? How many lives were lost? How much property damage? What was the impact of the eruption on the local and global landscape? Basically, why is the eruption notable?

Here is an example usage:

1980 eruption of Mount St. Helens
Photograph of the eruption column, May 18, 1980
火山Mount St. Helens
日期May 18, 1980
时间8:32 am PDT
类型Plinian
位置Skamania County, Washington
46°12′1″N 122°11′12″W / 46.20028°N 122.18667°W / 46.20028; -122.18667
VEI5
影响57 deaths, $1.1 billion in property damage; caused a partial collapse of the volcano's flank, deposited ash in 11 states
Map of eruption deposits

created with this source:

{{Infobox eruption
 | name = 1980 eruption of Mount St. Helens
 | image = MSH80 eruption mount st helens 05-18-80-dramatic-edit.jpg
 | image_size = 200px
 | caption = Photograph of the [[eruption column]], May 18, 1980
 | date = May 18, 1980
 | time = 8:32 am PDT
 | volcano = [[Mount St. Helens]]
 | type = [[Plinian eruption|Plinian]]
 | location = [[Skamania County, Washington|Skamania County]], [[Washington (state)|Washington]]
 | coordinates = {{coord|46|12|1|N|122|11|12|W|display=inline}}
 | VEI = 5
 | map = St helens map showing 1980 eruption deposits.png
 | map_size =
 | map_caption = Map of eruption deposits
 | impact = 57 deaths, $1.1 billion in property damage; caused a partial collapse of the volcano's flank, deposited ash in 11 states
}}

This template can also be used inside an article, in a section dedicated to an important volcanic eruption. In these cases, the volcano, location, coordinates, and map should be left out, as they are redundant to the main article infobox (presumably Template:Infobox mountain). For instance:

1914 eruption of Sakurajima
The city of Kagoshima was covered by deep ash during the 1914 eruption of the Sakurajima, which is visible across the bay.
日期January 1914
类型Peléan
VEI4
影响Pre-eruption earthquakes killed at least 35 people; caused an evacuation and significant changes to the local topology.

Source:

{{Infobox eruption
 | name = 1914 eruption of Sakurajima
 | image = Kagoshima 1914.jpg
 | image_size =
 | caption = The city of [[Kagoshima]] was covered by deep ash during the 1914 eruption of the Sakurajima, which is visible across the bay.
 | date = January 1914
 | time =
 | volcano = 
 | type = [[Peléan eruption|Peléan]]
 | location =
 | coordinates =
 | VEI = 4
 | map =
 | map_size =
 | map_caption =
 | impact = Pre-eruption earthquakes killed at least 35 people; caused an evacuation and significant changes to the local topology.
}}