Since 10 May, 2018, a significant number of volcanic and seismic events have been recorded in Mayotte, in the Comoros Archipelago of the Indian Ocean. Detailed bathymetry of Mayotte′s eastern regions has uncovered steep underwater slopes. A recent study in the area investigated liquefaction-prone layers associated with low sea-level depositions. However, the reason for the presence of such ‘weak zones’ remained unknown. In the present study, we examined samples from Mayotte’s slopes to investigate the reason for liquefaction at the particle-scale of such layers. Our results show that biogenic particles in naturally sedimented environments can crush under cyclic or static loading even with large amounts of fines. In the case of Mayotte’s slopes, the external loading threshold was found to be 500 kPa under K0-conditions. Our findings highlight the complex behavior of biogenic-dominant sediments, their impact on classification and overall behavior, and their potential implications for the design of wind farms.