Figure 74. (A) Aerial photo (1991) shows intra-island tidal channels in area of Moser Channel (lower middle Keys; Fig. 68B; from Lidz et al., 2003). White dotted line marks seaward edge of a nearshore rock ledge. Note tidal-delta sediments within channels or at channel edges. Bold dashed line is 1997 seismic Line 16 along the north edge of Hawk Channel. (B) Section of profile along north edge of Hawk Channel shows thin sediment cover and a large depression in main bedrock low under Hawk Channel (from Lidz et al., 2003). Seismic line is ~4.6 km south of and opposite Seven Mile Bridge crossing Moser Channel. Bedrock beneath the bridge is ~4.5 m
below sea level. Correlation of seismic profile with the photo and with a navigational chart (NOAA, 1993) indicates that the large seismic depression may be a deeper extension of the depression under Moser Channel. No seismic evidence of Knight Key Channel was visible in the part of the profile east of the section shown (along dashed line at right in A). 'Multiples' are an artifact common in seismic-reflection data. These reflections replicate those of existing, overlying, geologic surfaces and should not be regarded as representing any subsurface stratigraphic horizon. Latitude and longitude in degrees and decimal minutes based on GPS coordinates. Hours (military time) below coordinates serve as navigational correlation points along seismic line.