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).