Ruapehu volcano (North Island, New Zealand): gas flight observations; lake temperature is low
Thu, 22 Oct 2020, 07:5407:54 AM | BY: MARTIN
GeoNet observatory reported that the activity at Crater Lake (Te Wai ā-moe) is often dominated by a heating-cooling cycle. In the most recent cycle, the lake temperature reached a high of 41°C in April and then cooled steadily to 12 °C by late September. Over the last two weeks, the lake has warmed slightly to 15 °C, which is a normal observation.
Since the lake started cooling, a flight observations have been conducted to measure the flux of volcanic gases and lake water samples. Results from recent gas flights show variations in H2S (hydrogen sulphide), CO2 (carbon dioxide) and SO2 gas (sulphur dioxide). The SO2 and H2S are relatively stable while CO2 is decreasing from a high in May this year. This is consistent with more geothermal, than magmatic chemical reactions.
Crater Lake has two main submerged vents - North and Central vents. Observations of the lake over the last few months found that these vents were quiet. Late last week, a gas monitoring team observed clear upwelling and discolouration of the lake due to sediment mixing and bright yellow slicks of elemental sulphur over both vent areas. These observations and measurements all indicate that the underlying vent areas are open to volcanic gases and geothermal fluids entering the lake.
The level of volcanic tremor intensity has been variable but has remained weak during the past three months, and small earthquakes continue to be detected near the volcano.
Both the Volcanic Alert Level (level 1) and Aviation Code (Green) remain unchanged.
Source: GeoNet New Zealand volcano activity update 22 October 2020
Tue, 11 Aug 2020, 08:58
GeoNet observatory reported that since April 2020, lake temperature has decreased from a high of 42°C to around 22-23 °C. This lower lake temperature is normal for Crater Lake. To keep the lake at this temperature, low-level heat must continue to flow into the lake. This indicates that the underlying vent area is open to volcanic gases and hydrothermal fluids. Other signs that point to this open vent are visible upwellings and sulphur slicks on the lake surface. ... Read all