Geology topics

Research about Federated States of Micronesia

Source-linked reports with geographic coverage including Federated States of Micronesia.

15 recordsLinked to original sources

USGS2026

From start to stop: Simple methods for mapping susceptibility to landslide runout and debris-flow inundation

Landslide runout and debris-flow inundation can disrupt areas well beyond their initial sources, causing widespread damage and extensive fatalities. Understanding where they start and how far they might travel is essential in many locations worldwide. However, most landslide susceptibility maps focus on initiation areas and fail to incorporate runout areas. Furthermore, hazards vary greatly with the degree of landslide mobility, and debris flows can grow as they travel beyond their initial source. Here, we use the USGS Grfin Tools software suite to map susceptible areas from start to stop in the Federated States of Micronesia where landslide and debris-flows runout onto gentle ground is a deadly threat. The DEM-based models in Grfin Tools use simple, empirical, and well-documented approaches that require minimal parameters and, thus, can be used in areas that lack detailed physical properties. We illustrate methods to estimate the required parameters using direct landslide observations, and we suggest alternate methods if direct observations are absent. Our simple parameter estimations in the Federated States of Micronesia successfully predict areas that match past landslide runout and debris-flow inundation, as well as zones with no inundation. In addition to creating preliminary regional assessments, Grfin Tools can be used for comparing multiple scenarios and/or identifying areas for further investigations.

Chuuk, Kosrae, Pohnpei↗

USGS2024

Projecting mangrove forest resilience to sea-level rise on a Pacific Island: Species dynamics and ecological thresholds

Mangroves can increase their elevation relative to tidal flooding through biogeomorphic feedbacks but can submerge if rates of sea-level rise are too great. There is an urgent need to understand the vulnerability of mangroves to sea-level rise so local communities and resource managers can implement and prioritize actions. The need is especially pressing for small islands, which have been identified as an area of concern by the IPCC. We developed a generalizable modeling framework for tidal wetlands (WARMER-3) that accounts for species interactions and the belowground processes that dictate soil elevation building relative to sea levels. The model was calibrated with extensive field datasets, including accretion rates derived from 29 soil cores, over 300 forest inventory plots, water level, and elevation. The model included five mangrove tree species and was applied across seven regions around the Pacific Island of Pohnpei, Federated States of Micronesia, where mangrove forest is a critical ecosystem that supports subsistence living for local communities. We explored mangrove resilience and carbon accumulation under six sea-level rise scenarios. We also conducted an analysis to determine the sea-level rise rate threshold above which mangroves would be lost. The results suggest that Pohnpei mangroves can build their elevations relative to low and moderate rates of sea-level rise to prevent submergence, with limited loss of mangrove area through 2150. Under higher sea-level rise rates, however, forest elevation decreased substantially relative to mean sea level and there was extensive loss of mangrove area by that year. Regarding mangrove community composition, for all sea-level rise scenarios, the model predicted a change to increasing relative abundance of flood tolerant species and decreasing relative abundance of high-elevation species, which started to being realized by 2100. Variation in sediment supply, water levels, and elevation capital led to differential vulnerability around the island. We identified a threshold for Pohnpei mangroves where if local sea-level rise rates exceed 7.8 ± 2.2 mm/year they are projected to eventually submerge and be lost. Our modeling framework is novel by addressing both species interactions and critical belowground processes to better understand potential tidal ecosystem responses to sea-level rise.

Pohnpei↗

USGS2022

Elevations of mangrove forests of Pohnpei, Micronesia

Mangrove surface elevation is the crux of mangrove vulnerability to sea level rise. Local topography influences critical periods of tidal inundation that govern distributions of mangrove species and dictates future distributions. This study surveyed ground surface elevations of the extensive mangroves of Pohnpei, Federated States of Micronesia, integrating four survey technologies to solve issues of canopy blocking satellite reception, dense aerial roots limiting line-of-sight, and remoteness from surveyed datums. The island-wide average elevation of the mangrove seaward edge was −0.57 ± 0.13 m relative to MSL, while the landward average elevation was 0.33 ± 0.12 m relative to MSL. The overall mangrove elevation range was thus estimated to be 0.90 m. Mangrove species Bruguiera gymnorrhiza , Rhizophora apiculata and Sonneratia alba had large, overlapping elevation ranges, while Rhizophora stylosa occurred low in the tide frame. These species are likely to be less vulnerable to rising sea level given their greater range of elevation occurrence and presumably flooding tolerance, and hence have the highest adaptive capacity to rising sea level. Some landward edge species had very narrow elevation ranges, increasing their vulnerability to sea-level rise, with adjacent potential upland migration areas limited due to steep topography and human development. Pohnpei mangroves occupied 74% of the mean tidal range, similar to surveys elsewhere in the Pacific. This study demonstrates how more extensive understanding of the elevation distributions of intertidal species can contribute to sea-level rise vulnerability assessments, to allow prioritised climate change adaptation. However, more work is needed in standardizing approaches for global comparisons.

Estuarine, Coastal and Shelf Science↗

USGS2021

Using ALOS-2 synthetic aperture radar (SAR) and interferometric SAR to detect landslides on the mountainous island of Pohnpei, Federated States of Micronesia

This study was undertaken by the U.S. Geological Survey to assess the detectability of landslides in the densely forested and mountainous island of Pohnpei in the Federated States of Micronesia. The study used existing field-observed land-cover changes and landslides visible on Google Earth (GE) images. A limited number of ALOS-2 PALSAR-2 L-band synthetic aperture radar (SAR) images were collected on two adjacent orbit paths before and after an intense rainfall event that affected Pohnpei in mid-March 2018. Similar sets of images were collected in 2019 and 2020. Low coherence throughout the island interior eliminated use of phase-change products, and change analysis identified no landslide features as having formed in 2019 or 2020. The assessment of red-green-blue image composites and application of the log-ratio method to the 2018 ground-range SAR images identified 5 of the 11 landslides observed on the GE images. Visual comparisons of the co-event and post-event coherence image products detected 9 of the 11 landslides observed on the GE images. Combined, the ground-based SAR and interferometric SAR coherence change detections overcame high temporal and spatial decorrelations, identified all but one landslide visible in the GE comparison, and included substantial redundancy. The robustness of the landslide detection indicates that an increased collection frequency of L-band images could support systematic monitoring of land-cover change on Pohnpei at the scale reported in this study.

Island of Pohnpei↗

USGS2021

Mangrove species’ response to sea-level rise across Pohnpei, Federated States of Micronesia

Mangrove forests are likely vulnerable to accelerating sea-level rise; however, we lack the tools necessary to understand their future resilience. On the Pacific island of Pohnpei, Federated States of Micronesia, mangroves are habitat to endangered species and provide critical ecosystem services that support local communities. We developed a generalizable modeling framework for mangroves that accounts for species interactions and the belowground processes that dictate soil elevation. The modeling framework was calibrated with extensive field datasets, including accretion rates derived from thirty 1-meter-deep soil cores dated with lead-210, more than 300 forest inventory plots, water-level monitoring, and differential leveling elevation surveys. We applied the model using a community of five mangrove species and across seven regions around Pohnpei to identify which regions are most vulnerable to sea-level rise. The responses of mean elevation and the mangrove community composition were analyzed under four global sea-level rise scenarios: an increase of 37, 52, 67, or 117 centimeters by 2100. The model was validated against a 20-year surface elevation table record (1999–2019) and showed good agreement when driven by observed water levels. The model projected that mangroves around Pohnpei can build their elevations relative to moderate rates of sea-level rise to prevent submergence, with limited changes in mangrove community composition through 2060. By 2100, however, the model projected a decreasing abundance of high-elevation mangrove species and an increasing abundance of lower elevation species adapted to more persistent flooding. Under higher sea-level rise scenarios, forest elevation decreased substantially relative to mean sea level and there were more drastic changes in the tree community composition and loss of suitable mangrove habitat by 2100. Variation in accretion rates, water levels, and initial forest elevation led to differential vulnerability around the island, such that mangroves on the leeward side of the island generally were the most at-risk to higher rates of sea-level rise. Our findings indicate that the relatively undisturbed state of the mangrove forests and the surrounding landscape is an important factor in their ability to keep pace with sea-level rise.

Pohnpei↗

USGS2021

Microbial ecology of coral-dominated reefs in the Federated States of Micronesia

Microorganisms are central to the functioning of coral reef ecosystems, but their dynamics are unstudied on most reefs. We examined the microbial ecology of shallow reefs within the Federated States of Micronesia. We surveyed 20 reefs surrounding 7 islands and atolls (Yap, Woleai, Olimarao, Kosrae, Kapingamarangi, Nukuoro, and Pohnpei), spanning 875053 km 2 . On the reefs, we found consistently higher coral coverage (mean ± SD = 36.9 ± 22.2%; max 77%) compared to macroalgae coverage (15.2 ± 15.5%; max 58%), and low abundances of fish. Reef waters had low inorganic nutrient concentrations and were dominated by Synechococcus, Prochlorococcus, and SAR11 bacteria. The richness of bacterial and archaeal communities was significantly related to interactions between island/atoll and depth. High coral coverage on reefs was linked to higher relative abundances of Flavobacteriaceae, Leisingera, Owenweeksia, Vibrio, and the OM27 clade, as well as other heterotrophic bacterial groups, consistent with communities residing in waters near corals and within coral mucus. Microbial community structure at reef depth was significantly correlated with geographic distance, suggesting that island biogeography influences reef microbial communities. Reefs at Kosrae Island, which hosted the highest coral abundance and diversity, were unique compared to other locations; seawater from Kosrae reefs had the lowest organic carbon (59.8-67.9 µM), highest organic nitrogen (4.5-5.3 µM), and harbored consistent microbial communities (>85% similar), which were dominated by heterotrophic cells. This study suggests that the reef-water microbial ecology on Micronesian reefs is influenced by the density and diversity of corals as well as other biogeographical features.

Aquatic Microbial Ecology↗

USGS2015

Fine root productivity varies along nitrogen and phosphorus gradients in high-rainfall mangrove forests of Micronesia

Belowground biomass is thought to account for much of the total biomass in mangrove forests and may be related to soil fertility. The Yela River and the Sapwalap River, Federated States of Micronesia, contain a natural soil resource gradient defined by total phosphorus (P) density ranging from 0.05 to 0.42 mg cm −3 in different hydrogeomorphic settings. We used this fertility gradient to test the hypothesis that edaphic conditions constrain mangrove productivity through differential allocation of biomass to belowground roots. We removed sequential cores and implanted root ingrowth bags to measure in situ biomass and productivity, respectively. Belowground root biomass values ranged among sites from 0.448 ± 0.096 to 2.641 ± 0.534 kg m −2 . Root productivity (roots ≤20 mm) did not vary significantly along the gradient ( P = 0.3355) or with P fertilization after 6 months ( P = 0.2968). Fine root productivity (roots ≤2 mm), however, did vary significantly among sites ( P = 0.0363) and ranged from 45.88 ± 21.37 to 118.66 ± 38.05 g m −2 year −1 . The distribution of total standing root biomass and fine root productivity followed patterns of N:P ratios as hypothesized, with larger root mass generally associated with lower relative P concentrations. Many of the processes of nutrient acquisition reported from nutrient-limited mangrove forests may also occur in forests of greater biomass and productivity when growing along soil nutrient gradients.

Sapwalap River, Yela River↗

USGS2010

Climate change in the federated states of Micronesia: Food and water security, climate risk management, and adaptive strategies

This is a report of findings following research and a three-week field assessment (April 2009) of the Federated States of Micronesia (FSM) in response to nation-wide marine inundation by extreme tides (December 2007, September 2008, December 2008).3 The study was conducted at the request of the US Department of Agriculture Forest Service and the state and federal governments of FSM.

Report↗

USGS2004

Selection of arboreal termitaria for nesting by cooperatively breeding Micronesian Kingfishers Todiramphus cinnamominus reichenbachii

Limited nest-site availability appears to be an important factor in the evolution of delayed dispersal and cooperative breeding in some cavity-nesting species. The cooperatively breeding Pohnpei subspecies of Micronesian Kingfisher Todiramphus cinnamominus reichenbachii excavates nest cavities from the nests of arboreal termites Nasutitermes spp., or termitaria. In this first published description of nest-sites for this subspecies, we used surveys, remote sensing and radiotelemetry to evaluate the relationship between nest-site availability and co-operation. Results illustrate that nest termitaria are higher in the forest canopy, larger in volume and occur in areas with more contiguous canopy cover than unused termitaria. Nest termitaria were selected independently of the proximity to forest edges and territory boundaries, and we found no difference in characteristics of termitaria used by cooperative groups and breeding pairs. Logistic regression modelling indicated that termitaria with nest-like characteristics were not limited in abundance, suggesting that neither the prospects of inheriting nesting resources nor limited nest-site abundance are probable explanations for delayed dispersal in the Pohnpei subspecies of Micronesian Kingfisher.

Pohnpei↗

USGS2004

Hazard analysis of landslides triggered by Typhoon Chata’an on July 2, 2002, in Chuuk State, Federated States of Micronesia

More than 250 landslides were triggered across the eastern volcanic islands of Chuuk State in the Federated States of Micronesia by torrential rainfall from tropical storm Chata’an on July 2, 2002. Landslides triggered during nearly 20 inches of rainfall in less than 24 hours caused 43 fatalities and the destruction or damage of 231 structures, including homes, schools, community centers, and medical dispensaries. Landslides also buried roads, crops, and water supplies. The landslides ranged in volume from a few cubic meters to more than 1 million cubic meters. Most of the failures began as slumps and transformed into debris ﬂows, some of which traveled several hundred meters across coastal ﬂatlands into populated areas. A landslide-inventory map produced after the storm shows that the island of Tonoas had the largest area affected by landslides, although the islands of Weno, Fefan, Etten, Uman, Siis, Udot, Eot, and Fanapanges also had signiﬁcant landslides. Based on observations since the storm, we estimate the continuing hazard from landslides triggered by Chata’an to be relatively low. However, tropical storms and typhoons similar to Chata’an frequently develop in Micronesia and are likely to affect the islands of Chuuk in the future. To assess the landslide hazard from future tropical storms, we produced a hazard map that identiﬁes landslide-source areas of high, moderate, and low hazard. This map can be used to identify relatively safe areas for relocating structures or establishing areas where people could gather for shelter in relative safety during future typhoons or tropical storms similar to Chata’an.

Chuuk State↗

USGS2001

Maximum longevities of Rhizophora apiculata and R. mucronata propagules

The longevity of viviparous mangrove seedlings (propagules) in seawater is a key factor determining their ability to survive dispersal both locally and across large expanses of ocean. The purpose of this experiment was to determine the maximum longevities of propagules from two common Pacific mangrove species: Rhizophora mucronata Lamk. and Rhizophora apiculata Bl. Propagules from each of these species were placed in outdoor tubs with continuously flowing seawater. The condition of each propagule was monitored until it sank or started to rot. Propagules were then planted to determine viability. After planting, 50% of R. apiculata propagules and 21% of R. mucronata propagules were viable. For both species, mortality of propagules was strongly related to the length of the floating interval. Maximum longevities for R. mucronata and R. apiculata propagules were 150 (median = 70) and 89 days (median = 7), respectively. Rhizophora mucronata propagules appeared to be better equipped for long-distance dispersal, yet had low survivorship that would decrease overall dispersal opportunities. In comparison, R. apiculata propagules had higher survivorship yet shorter longevity and, thus, appeared to be better equipped for shorter distance dispersal.

Kosrae↗

USGS1996

Hydrogeology and ground-water resources of Pingelap Island, Pingelap Atoll, State of Pohnpei, Federated States of Micronesia

The lens of fresh ground water on Pingelap Island, Pingelap Atoll contains about 384 million gallons of potable water. Recharge to the freshwater lens is estimated to be 230,000 gallons per day on the basis of an average annual rainfall of 160 inches. The long-term average sustainable yield is estimated to be about 69,000 gallons per day. The estimated demand for water is about 50,000 gallons per day. Shallow-vertical-tube wells or horizontal-infiltration wells could be used to develop the freshwater lens. The effect of development on the lens can be determined by monitoring the chloride concentration of water from a network of shallow-water-table wells and deep driven wells. The ground-water resource on Pingelap can be used in conjunction with individual rainwater-catchment systems: rainwater can be used for drinking and cooking, and ground water can be used for sanitary uses. When rainwater-catchment systems fail during extended dry periods, ground water would be available to meet the total demand.

State of Pohnpei↗

USGS1996

Water-quality reconnaissance of ground water in the inhabited outer islands of Chuuk State, Federated States of Micronesia, 1984-85

A reconnaissance of ground-water quality in 24 inhabited outer islands in Chuuk State was made between January 1984 and October 1985. Most of the islands are part of low-lying coral atolls within the Western, Namonuito, Hall, and Mortlock Island Groups. A total of 648 wells were located and sampled for temperature and specific conductance. A few miscellaneous sites such as taro patches also were sampled. The nitrate concentration was determined for 308 water samples. To develop a relation between specific conductance and chloride concentration, the chloride concentration was determined for 63 water samples. In addition, 21 water samples were analyzed for major and trace constituent ion concentrations. Chloride and nitrate are the primary constituents affecting the potability of ground water in the inhabited outer islands of Chuuk State. The source of chloride in ground water is seawater, whereas nitrate is derived from plant and animal waste materials. The chloride concentrations in many well waters exceed the World Health Organization guideline for drinking water, particularly in wells near the shoreline or on small islands. In addition, the nitrate concentrations in some well waters exceeded the World Health Organization guideline for drinking water.

Chuuk State↗

USGS1987

Macrofauna and environment of the Nanpil-Kiepw River, Ponape, Eastern Caroline Islands

The first comprehensive evaluation of stream fauna in the Eastern Caroline Islands resulted from collections on Ponape, a 334-km- island having more than 40 streams, many of which arise along 700-m-high interior ridges. Field surveys centered on the Nanpil-Kiepw River below 170 m elevation, a bouldery reach with water of low mineral content and frequent surging flows. Faunal specimens were collected by electrofishing, rotenone treatment, netting, and hand picking. Discharge character of the Nanpil-Kiepw River is similar to but more extreme than that of other streams of Oceania with which it was compared. Drastic flow surges appeared to be a major factor affecting community structure. At least 44 faunal species were present, 36 of them representing taxons primarily of marine origin that are characteristic of oceanic islands: 15 fishes (5 families), 10 decapod crustaceans (3 families), and 11 snails (2 families). Larvae of aquatic moths were the only insects of significance. Four sicydiine gobies are new species possibly endemic to Ponape or the Eastern Caroline Islands. Based on numbers of species within prominent taxons and diadromous groups, Ponape’s faunal diversity exceeds that of Samoa, Guam, and Hawaii, but is lower than that of Palau. Similarities of Ponape's identified fish species to those of Palau suggest that Ponape was colonized from the west along the “Caroline conduit.”

Pohnpei↗

USGS1958

Geology of Kapingamarangi Atoll, Caroline Islands

Kapingamarangi Atoll of the Caroline Islands consists of a peripheral reef, 1000-4000 feet across, surrounding a nearly circular lagoon which is 5 by 6 nautical miles in area and about 240 feet at maximum depth. Thirty-three islands, most of which are less than half a mile in length, are scattered along the eastern half of the peripheral reef. At least 75 patch reefs, most of which are small, nearly symmetrical mounds, rise to the surface of the lagoon. The peripheral reef and the patch reefs, composed largely of the stony structures of corals and coralline algae, have flat upper surfaces, apparently the result of bevelling by waves during a recent lowering of sea level. The islands on the peripheral reef are formed of partially consolidated stratified sediments composed of clastic limestone particles and the shells of marine animals. These islands are migrating lagoonward across the reef flat because of erosion on the seaward sides and the growth of beaches and bars on the opposite sides. Soils on the islands are poorly developed and retain much of the texture, structure, and composition of the parent rock or sediment. They consist chiefly of mechanical mixtures of carbonaceous material and lime gravel, lime sand, or lime mud. Phosphorite is present on some islands and is still forming locally where apatite derived from bird guano is reacting with limestones. The tidal fluctuation of ground-water lenses, determined on islands of several sizes, ranges from about 4 to 18 inches. In one very small island where the water is brackish, the rise is much greater. The time lag between tidal movements and the rise and fall of fresh water in the islands ranges from a few minutes on very small islands up to 5 hours on some large ones. This time lag is controlled by the permeability of rocks composing an island and varies from one area to another according to the distribution of rock types. The lagoon contains six concentric belts of bottom sediment; in each, the composition and texture depend on the depth of water in which it occurs. Lime sand and lime gravel derived for the most part from the shells of animals form most of the sediment, but a lime mud covers the bottom of the deepest parts of the lagoon. Waves and currents cause gradation between types of sediment to a depth of about 30 feet, but little mixing was detected at greater depths.

Kapingamarangi Atoll, Caroline Islands↗