Pasuquin Carbonate Boulders
Description
This dataset contains the location, morphometry measurements, minimum flow velocity, and minimum wave height of the carbonate boulders in Barangay Davila and Dilavo, in Pasuquin Municipality, Ilocos Norte Province, Philippines. One of the objectives of the research is to characterize the extreme wave event (EWE) (tsunami or storm surge) that deposited the boulders by measuring the boulder morphometry, spatial distribution, and employing hydrodynamic modeling (Nandasena et al., 2022; Pignatelli et al., 2009; Shah-hosseini et al., 2011). The hydrodynamic model calculates the minimum flow velocity (MFV) and minimum wave height (MWH) of the extreme wave event that could initiate boulder movement. The boulder morphometry includes the boulder axes (long, intermediate, and short), mass, volume, density, and shape. The spatial distribution partly includes the boulder orientation and distance from shore. The data required by the hydrodynamic model are: the boulder axes measurements, boulder volume, seawater volume, gravitational acceleration, coefficient of virtual lift (Nandasena et al., 2022), coefficient of virtual drag (Imamura et al., 2008), coefficient of friction (Nandasena et al., 2011), coefficient of virtual volume, and slope of platform. Boulder axes, boulder volume, and platform slope were measured in the field. The coefficient of virtual volume was calculated using the boulder measurements. The other coefficients were determined from literature. The MFV has two scenarios based on the boulder pre-transport setting: the subaerial/submerged scenario (SS) and the joint-bounded scenario (JBS). The SS has three transport mechanisms: sliding, rolling, lifting. The transport mechanism of JBS is lifting only. The MFVs were also calculated using a range of values for the coefficient of lift to demonstrate how the wave type (e.g. supercritical, subcritical, critical) of the EWE may have affected the boulder deposition. The MWH has two scenarios based on the wave type parameter (δ): δ = 4 (Pignatelli et al., 2009) and δ = 1 (Shah-hosseini et al., 2011). Similar to the MFVs, the MWHs were also calculated using a range of values for the coefficient of lift to demonstrate how the wave type (e.g. supercritical, subcritical, critical) of the EWE may have affected the boulder deposition. The findings show that: 1) Increasing the coefficient of lift results in a lower MFV and MWH. 2) Sliding and rolling have similar MFVs in Pasuquin, indicating that the primary transport mechanism of the boulders are rolling or lifting. 3) The measurements in Pasuquin are comparable to the global occurrences of boulders.
Files
Steps to reproduce
1. Measure the long, intermediate, and short axes of the boulders. Measure the distance from shore and the trend of the boulders. Measure the slope angle of the platform. 2. Calculate the density by measuring the mass of representative boulder sub-sample and dividing it by its volume. The volume of the sub-sample can be obtained through the water displacement method. 3. Calculate the mass of the whole boulder by multiplying the density calculated from the sub-sample and the volume of the whole boulder, measured based on a best-fit ellipsoid model. 4. Calculate the shape indices (Blott and Pye, 2008) and plot in a Zingg diagram. 5. Calculate the minimum flow velocity (MFV) (Nandasena et al., 2022) for the subaerial/submerged boulder (sliding, rolling, lifting) and joint-bounded boulder (lifting) scenarios. Calculate the MFVs using three different values for the coefficient of lift (0.1, 0.45, and 0.8). 6. Calculate the minimum wave height (MWH) for the δ = 4 (Pignatelli et al., 2009) and δ = 1 (Shah-hosseini et al., 2011) scenarios. Calculate the MWHs using three different values for the coefficient of lift (0.1, 0.45, and 0.8). 7. Present the data in an open-high-low-close graph in Excel.
Institutions
- University of the Philippines Diliman National Institute of Geological Sciences