Figure 13: Schematic models describing how pit crater may be expected to relate to different dyke processes. (A) Pit crater formation is linked to lateral propagation of the dyke tip, perhaps driven by fluid escape into and/or collapse of the tip cavity, or eruption (Hughes et al., 2018; Scott & Wilson, 2002). Pit crater age decreases further from the dyke source. (B) Pit crater formation occurs as the dyke widens behind the propagating tip, perhaps linked to tensile fracturing (Tanaka & Golombek, 1989) as dyke widening induces extension of the overlying rock, fluid escape into and/or collapse of the tip cavity, or eruption (Hughes et al., 2018; Scott & Wilson, 2002). Pit crater age decreases further from the dyke source. (C) Pit crater formation occurs as the magma driving pressure or supply wanes, causing magma to flow backwards (e.g., Philpotts & Asher, 1994) and/or solidify and contract (i.e. a volume reduction) (e.g., Caricchi et al., 2014). Pit crater age increases further from the dyke source.
Pit crater depth
Where pit craters are observed on the surface of Earth and other planetary bodies, we are typically restricted to measuring their plan-view geometry (e.g., axial dimensions) and crater depth (e.g., Whitten & Martin, 2019; Wyrick et al., 2004). Numerous studies have demonstrated that pit crater depths of most populations likely related to dyke or fault activity, positively correlates with their long axis length via power-law relations (R2 = 0.45–0.90) with similar slopes (Fig. 12C) (e.g., Ferrill et al., 2011; Gwinner et al., 2012; Kling et al., 2021; Okubo & Martel, 1998; Scott & Wilson, 2002; Whitten & Martin, 2019; Wyrick et al., 2004); all these data can be fit by a power-law relationship (R2 = 0.94; Fig. 12C). Some pit craters within the Golan volcanic province, southern Levant, are an exception to this power-law trend as they show no correlation between pit crater depth and long axis, which has been attributed to recent modification by erosion and sedimentation (R2 = 0.05; Fig. 12C) (Frumkin & Naor, 2019).
From our seismic reflection data, we can measure pit crater morphometric properties, but we first need to establish whether the height of the inverted cone sections we describe, or that of the deflected reflections they contain, are equivalent to pit crater depth (Fig. 3B). For pit craters above dykes, dyke-induced faults, and tectonic faults, we find that cone height and pit long axis length positively correlate (R2 = 0.61, 0.24, and 0.77, respectively) and overlaps with data from many other locations (Fig. 12C). However, there is no meaningful correlation (R2 = <0.1) for deflection height and pit long axis length (Fig. 12C). The deflection height measurements also fall an order of magnitude below the power-law trend fit to the compiled published pit crater data; this is similar to pit craters in the Golan volcanic province and Noctis Labyrinthus (Mars), both of which display evidence for post-formation modification of their initial geometries (Fig. 12C) (Frumkin & Naor, 2019; Kling et al., 2021). Based on these comparisons, we suggest that the walls of the inverted cone sections represent the original pit crater morphology (Fig. 14). The reflections within the inverted cone sections are interpreted to correspond to material that infilled the pit crater (Fig. 14). Our results support recent suggestions that relationships between pit crater depths and long axis lengths may provide some indication as to whether post-formation erosional and infilling processes have modified pit geometry (Figs 12C and 14) (Frumkin & Naor, 2019; Kling et al., 2021).