MaarVLS 2.0 database

Categories include: 

Name = Name of crater used in published literature. Alternate names are included in parentheses, not exhaustive. When no name was available the crater is referenced numerical with an abbreviation of the volcanic field name, or reference to closely neighboring maar. 
Alternative name = Alternate name of individual crater or volcanic field.
GVP Number = Global volcanism number, when available, for individual crater or volcanic field.
Shape Type = SHP or Polygon. This value reflects whether the shape was produced using Google Earth imagery, ArcGIS, or QGIS.
Area = area of crater outline in km^2.
Perimeter = area of crater perimeter in km.
Latitude = Latitude of center of crater outline polygon (WGS84).
Longitude = Longitude of center of crater outline polygon (WGS84).
Country = Country where the crater is located.
Land Use = Generalized modern land use around crater.
Major Diameter = Major axis of crater outline polygon in meters.
Minor Diameter = Minor axis of crater outline shape in meters, must cross through centroid and be perpendicular to Major diameter.
Average = The average of Major and Minor Diameters.
Aspect Ratio = Minor Diameter (d2) / Major Diameter (d1), value decreases away from one as the shape deviates from circular.
Elongation = Major Diameter (d1) / (area/Major Diameter (d1)), value increases away from 1.27 as the shape becomes more elongate.
Isoperimetric circularity = (4* pi * area)/ perimeter ^2, value decreases away from one as the shape deviates from circular.
Volcanic Field type = Three categories are used: Complex Volcanic Field, Small Volcano Field and Alone. Complex fields contain a wide range of volcano types and volumes, small volcanic fields contain only small volume volcanic edifices such as scoria cones, small shields, and maars.
With other maars = Three categories are used: no, few and yes. Few indicates less than five maars in the same volcanic field. Yes indicates five or more maars in the same volcanic field.
Field Name = Most commonly used name assigned to the volcanic field in the literature, not exhaustive.
Multiple eruptions = When sufficient field data is published regarding the stratigraphy of the tephra ring to determine if the crater was produced by a single, or multiple eruptions separated in time. Not available for most craters yet. 
Underlying Geology = When available, host or bedrock substrate where maar occurs.
Tectonic setting = Limited categories modeled after Global Volcanism Program .
Elevation = Elevation of crater in meters, elevation of previous ground surface, or lake level (if present) +/- 50 m.
Depth = Depth of maar in meters from crater rim to floor, incomplete data is included with notes on whether it is rim, floor, or sediments.
Depth/Diameter = When available, values in italics are based on minimum depths.
Age = Age of eruption that formed the crater in years if available, or by period.
Composition = Composition of magma involved in the formation of the maar, as detailed as recorded in the literature.
Septum = Whether or not the crater contains a raised rim between multiple basins.
Pop 5km = Population estimated within 5 km of the volcanic field or crater based on 2013 GVP data.
Pop 100 km = Population estimated within 100 km of the volcanic field or crater based on 2013 GVP data.
References = Associated references for crater including peer reviewed papers, government informational websites, data sources and the Global Volcanism Program. Reference list is in a pdf document accompanying this database..