Quantifying lava temperature with a low-cost silicon-based thermal camera

An important characteristic quantity of volcanoes is the temperature of their magma. It depends on the magma composition, the volcanic activity, and partly affects the composition of magmatic gases that are later released to the atmosphere. Lava temperature measurements are thus desired for a manifold of volcanic studies at volcanoes including open magma-atmosphere interface (e.g. lava lakes).

The mostly used commercially available thermal cameras for the relevant temperature range (ca. 600-1200 °C) are still rather expensive, bulky, and have a limited spatial resolution.

We present an approach to use a compact (‘point and shoot’) consumer digital camera with a silicon based detector as a thermometer to record the spatial temperature distribution and variations of volcanic lava. Silicon detectors are commonly sensitive in the near infrared wavelength range (until ca. 1100 nm), which readily allows measurements of temperatures above ca. 500 °C. The camera is modified to block the visible spectrum and the remaining colour filter (Bayer filter) characteristics are used to infer the temperature from differential intensity measurements.

In the frame of this work, we performed a sensitivity study and calibrated the camera with a heated wire in the range of 600-1100 °C. Besides the advantages of the low costs, superior mobility and simple handling, the 16 megapixel spatial resolution of the temperature measurement allows resolving detailed temperature distributions in highly dynamic volcanic emission processes.