Energy Cone Model - a PDC Tool

The Energy Cone Model - At a Glance

Pyroclastic flows occur during some explosive volcanic eruptions. These flows are mixtures of hot gas, pyroclastic rocks and lithic fragments. Pyroclastic flows can travel at great speed and over great distance, depending on the proportion of gas in the erupting mixture. The mobility of the flow is often visualized using the Heim coefficient, H/L, the ratio of release height in the volcanic plume, H (the height of the crater or unstable eruption column above it), to total potential run-out length, L (how far the flow travels radially from the vent before it comes to rest). The radial distance and height create lines of energy that can be visualized as a cone in 3D, termed the energy cone, with the apex of the cone located at the release height above the vent and the base drawn as a circle around the vent indicating potential run-out length of the flow. The Heim coefficient was first introduced in volcano science by Mike Sheridan and his students around 1982.

The energy cone tool calculates potential run-out of pdcs using the Heim coefficient. The intersection of the base of the cone with the topographic surface controls potential run-out distance of the pdc from the erupting vent. This potential run-out distance, L is visualized by plotting the point of intersection on a topographic map. Several potential run-out distances can be calculated by the tool using a minimum release height and a maximum release height to bound the simulations. For a simplified demonstration of the energy cone model and the relationship of column height to run-out distance, check out this Menan Butte example.

Inputs

The Energy Cone tool expects the following input parameters:

• Digital Elevation Model (DEM) -- Choose a volcanic region from the pull down menu.
• vent location -- Specify the location of the erutping volcanic vent using an easting and northing in UTM coordinates. The vent must be located within the map region. If you chose UTM coordinates that are not within the map region, the simulation will not produce a result.
• minimum height, maximum height, interval -- Specify a range using a maximum height and minimum height of the erupting column (km above sea level) and choose an interval between them. This controls how many energy cones are drawn on your map. Use this feature to see how changes in the pdc release height H affect the run-out distance L, given topography in the area.
• H/L ratio or Heim coefficient -- This ratio controls the run-out length of the pdc L, given its release height, H and depending on the local topography. Typical H/L values range from 0.05 (highly mobile pdc) to 0.5 (low mobility pdc).
• minimum degree, maximum degree, interval -- Choose the entire energy cone (full circle around the volcanic vent: minimum = 0 degrees, maximum = 359 degrees) or only a part, to be plotted. The degree interval controls how many radial energy lines are calculated. A smaller interval will calculate more energy lines, leading to a higher resolution, but requires greater computation time.
• distance interval -- Choose a distance in meters where the check for intersection with topography is made along each radial energy line. This distance controls the frequency of calculations to determine one direction of total pdc run-out distance. A smaller distance interval causes more frequent checking (increased computation time), but results in a higher resolution map.

Run the Energy Cone Model »