Indonesian Journal of Earth Sciences

Analysis of Forest Cover in the Tumba-Lediima Nature Reserve (RTL-DRC)

Sylvestre Frey — 2025-02-11

This study analyzes the evolution of forest cover in the Tumba-Lediima Nature Reserve between 2010 and 2022, a period marked by increasing anthropogenic pressures. The main drivers of deforestation identified are agricultural expansion, illegal exploitation of forest resources and urbanization. These activities have led to the fragmentation of critical habitats, putting endemic and threatened species at risk, while also compromising the ecological integrity of the reserve. Furthermore, local communities face diminished livelihoods due to reduced access to natural resources. These dynamics lead to a critical loss of biodiversity, affecting critical habitats and compromising the livelihoods of local communities. Using Landsat 7 and 8 satellite imagery, combined with NDVI calculation and supervised classifications validated by a high Kappa coefficient, this study provides an accurate mapping of land cover change. The results reveal an alarming reduction in primary forest cover, accompanied by an increase in secondary forests and fallow land, suggesting limited potential for regeneration. This pattern underscores the urgent need to address the drivers of deforestation through targeted actions. These trends call for urgent conservation measures, including the targeted regeneration of degraded areas, the strengthening of environmental laws and the integration of local communities in the sustainable management of resources. By proposing concrete strategies in the short, medium and long term, this study offers essential perspectives for preserving the biodiversity and ecological resilience of the reserve. By proposing actionable strategies in the short, medium, and long term, this study provides a roadmap for preserving not only the biodiversity and ecological resilience of the reserve but also offers scalable solutions for similar tropical forest regions facing comparable challenges.

Spatial Variability and Analysis of Key Soil Properties in the Kesem Irrigation Scheme, Awash River Basin, Ethiopia

Mengistu Jiru — 2025-02-23

The Kesem Irrigation Scheme, located in the middle Awash River Basin of Ethiopia faces significant challenges due to widespread soil salinity and sodicity, hindering its agricultural productivity. This study aims to assess the spatial distribution and extent of soil salinity and evaluate the spatial variability of key soil properties in southern block of the scheme, encompassing 5000 hectares. A total of 154 composite soil samples were collected from both active sugarcane fields and abandoned areas at 0-30 cm and 30-60 cm depths. Soil properties analyzed included particle size distribution, pH, electrical conductivity (ECe), exchangeable sodium percentage (ESP), and exchangeable cations. Geostatistical analysis, including semivariogram modeling and ordinary kriging, was employed to assess the spatial variability of soil properties. Descriptive statistics, normality tests, and paired t-tests were performed. Soil textural classes were determined, and soil salt classes were classified based on ECe, ESP, and pH Soil texture analysis revealed a predominance of silt and clay fractions, while soil assessment identified four salt classes: non-saline, saline, saline-sodic, and alkaline based on FAO techniques. Results showed that pH had the lowest coefficient of variation (CV), while the ECe had the highest CV. Variability was generally greater in the bottom layer, except for cation exchange capacity (CEC) and ESP. Prosopis Julifera-infested areas had substantially lower ECe and ESP, with increased pH. Geostatistical analysis showed moderate to strong spatial dependence for most soil properties within a range of 861-6186 meters. The dominance of silt-dominated soils increases the risk of sodium retention, exacerbating salinity and sodicity issues. Elevated salinity and sodicity levels were observed in certain areas, attributed to factors such as groundwater table rise and inadequate drainage. This study provides valuable information for developing site-specific soil management strategies to enhance agricultural productivity and ensure sustainable agricultural land use. Further research is essential to determine the specific roles of various soil salinity factors in influencing soil properties within irrigated agricultural systems.

Noon-Time Thermal Comfort in a Tropical, Hot-Humid Climate City in the Philippines

Junelie Anthony Velonta — 2025-03-18

Climate change and urbanization will rapidly increase land surface temperatures in cities with tropical, hot-humid climates. Understanding how this increase affects the individual human requires gauging current thermal comfort levels. This study uses the Modified Physiologically Equivalent Temperature (mPET) model to quantify noon-time thermal comfort within the Dumaguete city center. Twenty locations were investigated. These areas were organized based on the overhead cover in each location: Green Cover (GC) for locations with vegetation providing shade, Artificial Cover (AC) for locations with cover made of artificial or constructed materials, and Sparse Cover (SC) for areas with direct sun exposure. mPET calculated for both the GC and AC locations all fall below the 44.09°C limit for Moderate Heat Stress. However, most SC locations exceed said limit, indicating Strong Heat Stress. SC locations within urban canyons exhibited the highest mPET of all locations, corresponding to the highest heat stress levels. Wind velocity reduced mPET on all locations, affecting AC areas the most. Mean Radiant Temperature (T_mrt), which accounted for the heat radiated by the infrastructure around an area, had the greatest influence on mPET. This study has found that thermal comfort is greatly affected by the density of infrastructure surrounding a location. Specifically, tall buildings close to each other reflect and concentrate heat towards the ground level, greatly degrading thermal comfort for pedestrians. These results could help inform future zoning laws, encourage the use of vegetation as overhead cover for footpaths, and advocate urban designs which capitalize on wind to ventilate populous areas.

Introduction of Ammonites from the Dalichai Formation in Polour Section Central Alborz, Iran

Masoomeh Sohrabi Mollayousefi — 2025-03-21

The studies done on Dalichai Formation in Central Alborz, South Polour Formation of an 80 m thick that are systematically sampled at intervals of 2 meters and selected the 40 rock samples for the preparation of thin sections considered and in addition to lithology; characteristics of the stone, and index examples of Ammonites were also studied. Dalichai formation lithology in the study area is rich in terms of alternating gray sandstone and marl with Ammonites Fauna. Based on the study of fossil fauna, the oldest identified ammonite in the studied section is Procerites (Early Bathonian), and the youngest is Reineckeia sp. (Late Callovian). The distribution of ammonites indicates that the eastern Alborz region had marine connections with northwestern Europe and the Mediterranean marginal areas during the Middle Jurassic period, and the study area was located north of the Tethys Ocean. Based on its stratigraphic position of the middle Jurassic Age Formation, Dalichai Ammonites with peer review study sections and microfossils Bathonian-Callovian age Dalichai is accurate. Lar Formation covers this formation with a gradual contact and has been parallel to the Shemshak Formation on an erosional unconformity. Through the examination of stratigraphy and the correlation of formations in the studied sequence, it was determined that the lower part of the Dalichai Formation is equivalent to other formations in Iran, including the Parvdeh Formation in the Shotori Mountains, the Kashfrood Formation in the Kopeh Dagh, and the lower part of the Baghamshah Formation in the Tabas Basin. The variations in thickness of the Dalichai Formation in the eastern Alborz region indicate relative subsidence of the sedimentary basin, a delay in sea-level rise, and the exit of sediments from seawater. These changes are indicative of the Middle Cimmerian tectonic event, which is observed as an erosional unconformity at the lower boundary of the Dalichai Formation.

Geotectonics and Exploration of Gold Mineralization in the Kushaka-Kusheriki Schist Belt North-Central Nigeria

Cyril C. Okpoli — 2025-04-14

The lack of systematic and organized development and exploration for gold and increasing demand for sustainable development goals has prompted the integrated geological, geophysical and geochemical surveys to characterize the gold mineralization at Owu part of the Kushaka-Kusheriki schist belt in North Central Nigeria. Previous studies concentrated on geology and geochemical studies with no emphasis on the use of integrated studies and state-of-the-art tools aimed at characterizing gold mineralization. Detailed geological mapping was carried out to determine the various rock types and their structural framework. Thirty- one (31) data were acquired using Proton Precession Magnetometer for geophysical survey to delineate their degree of magnetic susceptibility and dataset was enhanced using Fast Fourier Transforms (FFT). Inductively Coupled Plasma/Optical Emission Spectrometry (ICPOES), fire assay, multi-acid digestion with gravimetric method were carried out on rocks and soils to determine their geochemical signatures. Geologically, the study area consists of phyllite, mica schist, amphibole schist, phyllitic schist, biotite schist within schist shear zone. Structurally, granitic intrusions are observed in the NE-SW direction, parallel to the regional foliation of the rocks. Geophysical data were subjected to different forms of filtering, which showed high and low magnetic areas. The results reveal a distinct tectonic activity that led to shearing and fracturing, and subsequently gave rise to a structurally controlled mineralization pattern (i.e., NE-SW direction in the Pan African domain). ICPOES analysis yielded Au concentration of <0.2 – 201 ppm with 80% of the soil samples exceeding 2 ppm indicating their qualification as ores. The soil samples are enriched in W (1 – 241 ppm), Mo (1 – 19.8 ppm) but depleted in Sb (<5) and Ag (<2 ppm). Positive correlations between Au and Cu, Zn and Pb confirm that they are pathfinder elements for Au in the area. The geological and geophysical studies reveal structurally controlled mineralization; while the very low K/Ba (<0.01) suggests non- structurally controlled gold mineralization in sediments occasioned by dispersion of the metals. The integrated approach has proved effective in delineating gold mineralized zones, and is recommended for other related investigations.

Comparative Study on the Accuracy of Terrestrial and Global Gravitational Models (GGMs) Gravity Anomalies for Akure Environs, Ondo State, Nigeria

Ibrahim Olatunji Raufu — 2025-06-27

Spherical harmonic expansion is a mathematical method used to describe Earth's gravity field, derived from potential coefficients observed both on Earth's surface and from space. The International Centre for Gravity Earth Models (ICGEM) publishes Global Gravitational Models (GGMs), which require validation using terrestrial data to assess their suitability in specific regions. This study evaluates and compares gravity anomalies derived from five GGMs (EGM 2008, GECO, XGM2019e-2159, SGG-UGM-2, and EIGEN-6C4) with terrestrial gravity data over the Akure area of Ondo State, Nigeria. Gravity values and geodetic coordinates from 23 stations were analyzed. Terrestrial gravity data were sourced from previous field surveys, while GGM data were obtained from the International Centre for Global Earth Gravity Model (ICGEM). The study computed and compared free-air and Bouguer anomalies with mean differences ranging from -1.725 to 6.800 mGal (with standard errors between 1.058 to 1.965 mGal) for free-air anomalies, and -2.107 to 4.546 mGal (with standard errors between 0.773 to 1.041 mGal) for Bouguer anomalies. Statistical analyses revealed that the EGM 2008, GECO, and XGM 2019e-2159 models provided the best-fit with terrestrial measurements. These models can thus serve as reliable alternatives or complements to terrestrial gravity data for geoid determination in the Akure region. The study identifies EGM2008, GECO, and XGM2019e_2159 as the most suitable GGMs for geophysical applications in this area.

Flood Inundation Mapping and Spatial Analysis: A Case Study of the 2022 Massive Flood in Swat, Khyber Pakhtunkhwa, Pakistan

Atta Ullah — 2025-06-28

Climate change has increased the frequency of extreme precipitation, increasing rapid flood risks globally. This study integrates remote sensing, geospatial data and climatic statistics to map flood inundation and analyze precipitation patterns in Swat district, Khyber Pakhtunkhwa, Pakistan, following the 2022 flood. We used Google Earth Engine (GEE), applied supervised classification on sentinel-2 imagery achieving an accuracy of 99.7% for 2021 and 97.3% for 2022, confirming the precision of our analysis. Flood water body levels were meticulously scrutinized, culminating in the production of an illuminating flood inundation map through the Summer Permanent Water Bodies (SPWB) exclusion layer and Normalized Difference Flood Index (NDFI) framework. The NDVI and SPWB exclusion layer identified 1230 km² of inundated area and 258 km² of land use change in 2022. Analysis of Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) summer precipitation data revealed a peak of 877 mm in 2022, with significant increase in southern, central and northern parts of Swat. This study is an earnest attempt to advance our understanding of flood mapping and offer roadmap for enhanced disaster management, supporting urban planning and mitigation strategies in the flood prone regions of Swat.