Hyperspectral plant signatures can be used as a short-term, as well as long-term (100-year timescale) monitoring technique to verify that CO 2 sequestration fields have not been compromised. An influx of CO 2 gas into the soil can stress vegetation, which causes changes in the visible to near-infrared reflectance spectral signature of the vegetation. For 29 days, beginning on July 9, 2008, pure carbon dioxide gas was released through a 100-m long horizontal injection well, at a flow rate of 300 kg day -1 . Spectral signatures were recorded almost daily from an unmown patch of plants over the injection with a ''FieldSpec Pro'' spectrometer by Analytical Spectral Devices, Inc. Measurements were taken both inside and outside of the CO 2 leak zone to normalize observations for other environmental factors affecting the plants. Four to five days after the injection began, stress was observed in the spectral signatures of plants within 1 m of the well. After approximately 10 days, moderate to high amounts of stress were measured out to 2.5 m from the well. This spatial distribution corresponded to areas of high CO 2 flux from the injection. Airborne hyperspectral imagery, acquired by Resonon, Inc. of Bozeman, MT using their hyperspectral camera, also showed the same pattern of plant stress. Spectral signatures of the plants were also compared to the CO 2 concentrations in the soil, which indicated that the lower limit of soil CO 2 needed to stress vegetation is between 4 and 8% by volume.

a b s t r a c tThe March 13th 1888 collapse of Ritter Island in Papua New Guinea is the largest known sector collapse of an island volcano in historical times. One single event removed most of the island and its western submarine flank, and produced a landslide deposit that extends at least 70 km from the headwall of the collapse scar. We have mapped and described the deposits of the debris avalanche left by the collapse using full-coverage multibeam bathymetry, side-scan sonar backscatter intensity mapping, chirp seismic-reflection profiles, TowCam photographs of the seafloor and samples from a single dredge. Applying concepts originally developed on the 1980 Mount St. Helens collapse landslide deposits, we find that the Ritter landslide deposits show three distinct morphological facies: large block debris avalanche, matrix-rich debris avalanche and distal debris flow facies. Restoring the island's land and submarine topography we obtained a volume of 4.2 km 3 for the initial collapse, about 75% of which is now forming the large block facies at distances less than 12 km from the collapse scar. The matrix-rich facies volume is unknown, but large scale erosion of the marine sediment substrate yielded a minimum total volume of 6.4 km 3 in the distal debris flow and/or turbidite deposits, highlighting the efficiency of substrate erosion during the later history of the landslide movement. Although studying submarine landslide deposits we can never have the same confidence that subaerial observations provide, our analysis shows that well-exposed submarine landslide deposits can be interpreted in a similar way to subaerial volcano collapse deposits, and that they can in turn be used to interpret older, incompletely exposed submarine landslide deposits. Studying the deposits from a facies perspective provides the basis for reconstructing the kinematics of a collapse event landslide; understanding the mechanisms involved in its movement and deposition; and so providing key inputs to tsunami models.

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On the early morning of 13 March 1888, roughly five cubic kilometers of the Ritter Island volcano fell violently into the sea northeast of Papua New Guinea (Figure 1). This event, the largest lateral collapse of a volcanic island in historical time, flung devastating tsunamis tens of meters high onto adjacent shores [Cooke, 1981]. Calamitous as they might be, natural disasters like these must be viewed in perspective. One should ask, “Were the events of that March day unique, or are they common geological occurrences?” Partly to address this question, a seafloor imaging and sampling program was conducted around Ritter Island and elsewhere along the Bismarck volcanic arc during November–December 2004 on the research vessel Kilo Moana.

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