This interactive visualization animates contour lines of the volcano dataset, showing a smooth morphing effect as the contour thresholds transition between successive intervals. The display uses a plasma color scale to differentiate elevation bands, with white strokes delineating each path. The code constructs GeoJSON MultiPolygons from the gridded `volcano.json` data using `d3.contours` and projects them with `d3.geoNaturalEarth1` and `d3.geoPath`. A continuous loop drives a `transition` of 2000ms duration, interpolating threshold values and updating both the path shapes and fill colors to create a perpetual pulsing animation.