Geothermal

NASA comes to Rotorua

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Last week I was involved in a NASA Spaceward Bound meeting in Te Takinga Marae in Rotorua. The purpose of the meeting was to promote interest in Planetary Geology and  Astrobiology, and it was attended by about 50 scientists, educators, undergraduates and school students  from New Zealand, Australia, the USA, Romania, the UK and Kazakhstan.  Image:  NASA / JPL A large focus for NASA at present is the Curiosity Rover that has been exploring the surface of Mars for the last couple of years. One of the questions for the scientists is whether there are any traces of simple life forms in rocks on the surface. If found, these would show that whilst there may be no life at present on the red planet, it did manage to evolve there in the past under previous conditions. Image:  NASA / JPL In order to understand some of the geological features that are being observed using Curiosity’s various probes, it is useful to get to know comparable geological sites on the Earth’s surface that can be investigated and understood at close quarters. During the Spaceward Bound week we made several field trips to visit hot springs and volcanic landscapes in the Taupo Volcanic Zone. The focus of these trips was to see how microbial life can take hold in extreme physical environments such as very hot,  acidic geothermal springs, and to see how these living communities leave physical and chemical evidence of their existence (biomarkers) in the mineral formations that build up at these locations. This image shows a silica terrace at Waimangu volcanic valley. The colours are created by different species of microbes that thrive in these harsh conditions. The colour distribution shows the tolerance of particular species to different water temperatures.  For more about extremophiles in New Zealand find out about  the 1000 Springs Project. Extremophile microbes inhabit the hot mineral rich water that creates the rock formations at Pariki Stream, Rotokawa. The bacteria leave visible biomarkers in the sinter left behind as the mineral laden water evaporates. Parag Vaishampayan, a research scientist at NASA, took a close look. Quadcopter meets Rover at Rotokawa This small radio controlled rover was designed by Steve Hobbs at the University of New South Wales. It is adapted for remotely investigating hot springs, and includes a number of sensors such as spectrometers, a camera and a non contact thermometer. the quadcopter that you can also see in the picture has been adapted by Matthew Reyes, (a technologist at NASA) to scoop up water samples that can’t otherwise be easily accessed. Part of the field investigations included a study of plant colonisation of lava flows in the Mangatepopo Valley in Tongariro National Park. This photo shows a young lava flow on the slopes of Ngauruhoe volcano at the head of the valley. We also went on an excursion over the bare volcanic landscape of the Tongariro complex. Mars, as seen by Curiosity.            Image:  NASA / JPL For more information about astrobiology have a look at the New Zealand Astrobiology Initiative website, and to find out about Spaceward Bound New Zealand have a look here. Finally here is a news clip from TVNZ about Spaceward Bound, and an interview with AUT scientist Steve Pointing on National Radio.

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1000 Geothermal Springs

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GNS Science and Waikato University are investigating one thousand of the geothermal hot springs in New Zealand’s North Island. The goal of this ambitious 1000 Springs Research Project is to understand and compare the microbiology of these springs along with their physical  and chemical make-up. That adds up to a lot of sampling trips, processing of data and investigation of the findings! This video gives an overview of the different types of Geothermal Springs in the area: The GeoTrips website  www.geotrips.org.nz  includes lots of geothermal areas that you can visit such as this one at Waiotapu: www.geotrips.org.nz/trip.html?id=50 Some of these hot springs are scummy looking puddles like this one, that don’t seem to have much to say about themselves apart from the obvious message to stay clear and avoid being swallowed up by scalding mud. Bruce Mountain/ GNS Science Others are of course very spectacular and beautiful iconic tourist attractions such as the Champagne Pool at Waiotapu… A few days ago I joined some of the GNS Science team; Jean Power, Dave Evans and Matt Stott, (who leads the project)  on a sampling trip to Whakarewarewa village in Rotorua, The village is an extraordinary place, where a community has learnt to live in close relationship to an ever changing geothermal environment. Home heating, hot water, cooking and bathing is provided by the hot springs, although there are interesting downsides, such as occasional ground collapses and holes appearing next to houses Safety first! Investigating hot springs is a potentially hazardous activity. Sometimes well known and well trodden areas have suddenly caved in because the ground gets eroded from below. Scientists use various safety techniques as well as a strong sense of caution when approaching the springs. Dave Evans uses a long pole to reach into a hot pool to get a water sample, while Jean adds information to a tablet with an application that allows all the data to be quickly uploaded to the 1000 Springs database website.  Several water samples are taken, and the team measures the temperature, pH, conductivity, turbidity, dissolved oxygen and the redox potential of each spring, as well as taking photographs and other metadata. Geothermal ecosystems are globally rare and little is known about the unique populations of microorganisms (Bacteria and Archaea) that inhabit these environments or the ecological conditions that support them. Here Dave is carefully labellling the sample bottles. Samples are filtered and prepared for analysis after returning to the lab. To identify all the different species, the DNA in the sample is extracted and analysed, and the chemical content of the water and the dissolved gases is measured. Extremophiles are microorganisms that thrive in harsh environmental conditions – where temperatures can be as high as 122˚C, the pH can range from highly acidic to strongly alkaline, and there are elevated concentrations of salts and/or heavy metals. Different microbes are responsible for the spectacular colours seen in hot springs. The colour zonation relates directly to particular temperature ranges which the resident species have tolerance for. There are thought to be more than 15000 geothermal features in New Zealand, and each of them will have a distinct microbial community and often include many undiscovered species The selected springs span the known pH ranges (pH 0-9) and temperature ranges (20°C-99°C) or have unusual geochemical or geophysical profiles. Sites with high cultural or conservation value are also included. All this new knowledge will allow New Zealand to assess the conservation, cultural, recreational and resource development value of the microbes in geothermal ecosystems, and enable further future microbial ecology research and discovery. Photo by Matt Stott / GNS Science My role in these field trips is to visually document the scientific process and communicate about the research to all who are interested. Scientists are invariably passionate and enthusiastic about their work, and are keen for others to find out about what they do. Here is our video of the 1000 Springs team in action:

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The Hot Bed of Rotomahana

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This week I have been with Cornel de Ronde and a group of ocean floor researchers applying more of their methods to expand the large amount of research of Lake Rotomahana done over recent years. This is the lake that used to be decorated by the famous Pink and White Terraces. It was excavated by the extreme violence of the Mount Tarawera eruption in June 1886. This photo of a cliff section in the nearby Waimangu Valley, shows a black horizontal soil layer that was buried by volcanic mud during the eruption. The area still has a lot of geothermal activity. One of the tasks for this expedition was to measure the heat flow coming up through the lake floor. Scientists from Woods Hole Oceanographic Institution (WHOI), the National Oceanic and Atmospheric Administration (NOAA) and the University of Waikato collaborated with the project. Maurice Tivey of WHOI provided the special blankets for measuring heat flow in the ocean. This was the first time they had ever been used on a freshwater lake. The blankets have a thermistor (thermometer) on the top and the bottom. They measure the temperature on the surface of the lake floor sediment and also of the water layer just above. The difference between the two measurements allows the amount of heat flow to be calculated in watts / square metre (w/m2). The heat blankets are lowered on to the lake floor in a pre-determined grid pattern and left for 24 hours to equilibrate with the prevailing temperatures. Then they are pulled up to the surface and re-deployed in a new position. Gradually the whole lake floor gets coverage in this way with the 10 available blankets. The thermistors take readings of the temperature every minute and store the data until they are eventually plugged in to a computer for it to be downloaded. In the image you can see the temperature curves for a blanket that has been deployed at 4 different locations over 4 days. The upper curve shows the data from the lake sediment recorded by thermistor under the blanket. The lower, darker curve is the (cooler) water temperature recorded by the top thermistor. You can see that it takes several hours for the readings to adjust to the lake floor temperature conditions. The last recording on the right hand side is very hot, so the thermistor records a rising temperature. The dots on this map of Rotomahana show the locations of the measurements. Maurice has outlined the hot areas identified initially, although the data had still to be fully processed. You can see how the areas of high heat flow in the map above correlate well with the map of gas bubbles recorded on the surface of the lake in 2012. This may seem obvious for a hydrothermal system, but gas plumes are not necessarily accompanied by heat. This is a map of a heat survey that was undertaken in the 1990s. This week’s survey is more detailed and uses a new method,  but it will be interesting to see how the results compare. In the earlier survey, areas of heat flow of up to 10 w/m2 were outlined. Some of Maurice’s recordings are several times hotter than these. In this video. Maurice describes the new heat flow survey method:

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Rotomahana’s lake floor prompts many questions

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Following last weeks’ multibeam sonar survey, the bed of Lake Rotomahana has now been mapped to a resolution of half a metre, bringing to light a mass of detail hitherto unknown to scientists. The first photo shows last year’s map which was made with the assistance of WHOI (Wood’s Hole Oceanographic Institution). The resolution of the map is 15 metres.  This year, with the help of ixSurvey, we have improved that by 30x (second image). In this post I will show you some of the features that have come to light. The colour scale indicates depths in metres. Red represents the shallowest depths found around the shoreline, down to blue which is deepest in the main central part of the lake. The maximum depth is about 115 metres. The grey area is the land around the lake that is above water level, or very shallow parts of the south side of the lake that were not scanned. Click on the image for a larger view. The map we now have allows close up study of many fascinating features that we can see for the first time. In the third image showing the northern margin of the lake, you can see two explosion craters right on the very edge. They are about 25 metres deep. In the bottom right part of the image is a newly revealed crater, formed at a late stage in the 1886 eruption. Its rim is about 60 metres below the surface, and its floor is at about 80 metres. All of these craters are approximately 100 metres across. If you click on this image of the flat, deepest part of the lake (blue area), you might just discern a faint circular feature just below and to the right of centre. This is also about 100 metres across and may be the outline of a crater rim that has been almost totally obscured by mud, or it may be the lobe shape of a debris flow that cascaded down from the north, leaving a smooth gouge  in the slope (upper part of the picture). In the lower (southern) part of the map there are many erosion features visible on the sloping lake floor. On the left of this image you can see some eroded gullies  extending down from the red area (-20m) into the blue (-100m). We believe these runnels formed in the few years after the Tarawera eruption, before the lake filled up, rather than that they were eroded after the water level rose. On the right hand side of the image, there is another area of radiating features. These have quite a different character, being less smooth, and with intriguing lines of hollows. These may have formed as a result of the wave like flow of debris down the slope, but we are uncertain as to why they are so different to the features just to the left (west). The southern half of the blue area on the map has a lot of gas activity. This was noticed last year on some of the sidescan images showing plumes of bubbles arising from a pick marked area on the bed of the lake. This activity has increased dramatically in this part of the lake floor since the Tarawera eruption. Now we can see this area of hydrothermal and gaseous activity in detail, with the ‘pock marks’ showing up as a mass of small vents scattered over a wide area. These are each up to a few metres across. A very significant feature that was revealed in last years’ bathymetric map was the ‘spit’ or promontary that is shown on early photographs of the Pink Terraces. It is extending into the lake in the middle distance of this photograph, not far to the east of the Pink Terraces visible in the left foreground. The spit rises several metres above water level. (Image courtesy of the Alexander Turnbull Library, Wellington) On our new bathymetric map we can clearly see the promontary, now with its crest below 50 or 60 metres of water.

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Rock in the Boat

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Along with biological specimens, the sled brings a lot of rock off the sea floor. Christian Timm sorts through all the samples, cuts some of them up with a rock saw, and packs and labels them to be studied in detail back at GNS Science. The different minerals present in the samples will be analysed to give detailed information about the processes occurring deep down in the collision zone where the Pacific and Australian plates meet, as well as about the hydrothermal alteration of the rocks at the sea floor. Here is a selection of examples from off the cone of Rumble 2 West volcano that we have been checking out for the last few days: First up is a piece of volcanic rock (basalt) that comes from the cone of Rumble 2 West. It would have cooled rapidly as it encountered the sea water, which has preserved the flow structure running through the centre of the specimen. Hydrothermal fluid contains a lot of iron that it has dissolved from the basalt it has passed through down in the crust. As it reaches the sea floor and cools, it precipitates out the iron as an oxide called haematite, which has a deep red colour. Silicon is the most common element in the earth’s crust, along with oxygen with which it combines as silica (quartz). There are many other siliceous minerals too, some of which are precipitated around hydrothermal vents in association with microbes. These yellow and orange pieces contain several types of silica with different quantities of trace elements that give a wide colour range. The whitish stripes in this piece of basalt are from small crystals of barium sulphate or barite. As sea water flows down into a seamount and heats up, it loses a lot of calcium sulphate which precipitates out. The hot, sulphate poor fluid then dissolves barium from the surrounding rocks, bringing it back up to the sea floor. The barium then combines with the sulphate in the fresh sea water to give rise to these barite crystals. They tell us that hydrothermal fluids have been cycled through the crust in this area, and can even be dated to give a timescale for the process. This small piece is a jam packed mixture of rock fragments and minerals. It It is part of the debris from an old broken up black smoker chimney. It is loaded with valuable metal rich compounds that have crystallised as the hot hydrothermal fluid gushed out into the surrounding sea water.  Cornel de Ronde is checking out the finds and explaining some of their features to crew member Peter Morrison.

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Hot Water Plumes

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Hydrothermal activity in undersea volcanoes is largely the result of sea water descending into the crust, being heated up and then chemically breaking down the surrounding rocks as it rises back up to the sea bed. These mineral rich fluids then re-enter the water column either diffusely over a wide area, or out of one of many vents in a hydrothermal field. As the emerging hydrothermal fluids mix with the sea water and quickly cool down, the dissolved minerals within them precipitate out. Some (such as metal sulphides) will accumulate immediately around the vent to create vertical chimney like structure, whilst others (such as iron and manganese oxides) will form particles that get carried up in the hot water plume to form a sheet like cloud that is pulled sideways by water currents. The particles within the cloud will slowly rain out back to the sea floor over a wide area. Sharon Walker from NOAA (the National Ocean and Atmosphere Administration in the US) specialises in analysing the physical and chemical properties of sea water to locate hydrothermal plumes and the vents that have created them. She uses several tools mounted onto a CTDO (conductivity, temperature, depth and optical) recording device. In the photo you can see Cornel de Ronde and Matt Leybourne preparing the CTDO. It will be towed below the ship and lifted up and down to sample at different depths. On it there is a light scattering sensor which detects reflected light to give a measure of the water’s particle content. It will also take samples of water from different levels in the water column for chemical analysis. Yesterday Sharon and Matt collated some results to create this diagram of the hydrothermal plume above Rumble 2 West volcano. The green and yellow lines represent light scattering. You can see that near the bottom there is a large spike indicating a hydrothermal plume about 30 metres thick. Faint red lines across the graph show the depths at which water samples were taken. Finally here is a photo I took from the bridge during quite windy and choppy conditions the day before yesterday, just to show that it is not always flat as a mirror out here. For some of us landlubbers it meant spending a bit of time outside looking over the rail… just admiring the view of course.

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