Water Fountain Speed and Height at Strokkur Geyser, Iceland, derived from Video Camera Data

Strokkur geyser in Iceland is located in the Haukadalur valley, Iceland. It exhibits frequent, jetting eruptions of hot water and non-condensable gases such as CO₂. In earlier studies we found that Strokkur geyser erupts at regular intervals and passes through typical phases in an eruptive cycle. This eruptive cycle consists of the eruption, conduit refilling with water, gas accumulation in a bubble trap and regular bubble collapses at depth in the conduit. In this presentation we focus on the blue bulge that forms at the beginning of an eruption and the water fountain itself.

To study this, we use video camera data from 2017 and 2020 in comparison with a local broadband seismic network. We assess the bulge height, fountain height, the bulge rising speed, water fountain rising speed and the associated seismic amplitude. Particularly, ImageJ with the MtrackJ plugin was used to assess the bulge height and fountain height. We find that upto 0.5 m high water bulge forms within 0.7 s at an average speed of 0.6 m/s. Water is then expelled into the air at a speed of 10 m/s reaching heights of up to 40 m. We compare the speeds measured on the surface with (i) expected rising speeds of gas bubbles in water given a certain diameter and (ii) migration speeds derived from migrating seismic source locations. We discuss the derived height with respect to seismic amplitudes to constrain the tremor generation and to finally assess whether the seismic amplitude (e. g. RMS) has any predictive power when it comes to eruption forecasting.