Departed Apia 1300L/22, 45 hours late 'cos of our return to port to pick up co
P.I. and essential STS gear (DR plotter now working), and to tend to sick crew
member. Port stop took a few hours longer than expected 'cos of Samoa Prime
Minister's funeral, finding a medical doctor etc. Castillo and I request that 2
days be added to the end of this leg (i.e. change ETA to 14 April) to compensate
for lost time. This will cause a few of us (but not any/many others?) extra
hassle and expense of changing plane tickets, but we can cope. Peter Lonsdale

R/V Melville, Weekly Scientific Report, AVON Leg 4, 29 March 1999: Have spent
the past week surveying the fault scarps produced by Active deformation of the
outer slope of the Tonga Trench, and dredging the igneous rock exposed on these
scarps. Program had been proceeding well, but has been abruptly terminated on
orders of the Captain because a depresScrippsn with 20-25 knot winds is
threatening to move into the trench. At present running away from our work area,
toward the northwest. (Peter Lonsdale/Scripps)

Subject: AVON 4 WEEKLY REPORT Have spent the past week surveying the fault
scarps produced by active deformation of the outer slope of the Tonga Trench,
and dredging the igneous rock exposed on these scarps. Program had been
proceeding well, but has been abruptly terminated on orders of the Captain
because a depression with 20-25 knot winds is threatening to move into the
trench. At present running away from our work area, toward the northwest. Peter
Lonsdale

R/V Melville, Weekly Scientific Report, AVON Leg 4, 13 April 1999: Heading
(vaguely) back to Apia, Samoa, after surveying and sampling 2000km of outer
slope and outer rise of the Tonga-Kermadec Trench. Dredging active fault scarps
that are being made by extenScrippsnal bending of the crust at the top of the
outer slope proved an effective way of collecting fresh (and rotten) samples of
the Cretaceous igneous crust--- raised from 6500-8500m depths at record speed
(70m/min) by Melville's revamped main winch. The fault scarps, some of which
bound graben more than 1 km deep, have intricate sinuous and branching patterns
(mapped with SEA BEAM); they are generally orthogonal to the pre-existing
abyssal hill faults, but are influenced by major features ofthe subducting
plate, such as fracture zones and hotspot volcanoes. Our seismic profiling
showed only 100-150m of sediment cover on most of the subducting plate, except
for the aprons of hotspot volcanoes and Pacific Bottom Water drifts along the
southern Kermadec Trench. (Peter Lonsdale/Scripps)


Heading (vaguely) back to Apia, Samoa, after surveying and sampling 2000km of
outer slope and outer rise of the Tonga-Kermadec Trench. Dredging active fault
scarps that are being made by extensional bending of the crust at the top of the
outer slope proved an effective way of collecting fresh (and rotten) samples of
the Cretaceous igneous crust --- raised from 6500-8500m depths at record speed
(70m/min) by MELVILLE's revamped main winch.The fault scarps, some of which
bound graben more than 1 km deep, have intricate sinuous and branching patterns
(mapped with Seabeam); they are generally orthogonal to the pre-existing abyssal
hill faults, but are influenced by major features of the subducting plate, such
as fracture zones and hotspot volcanoes. Our seismic profiling showed only
100-150m of sediment cover on most of the subducting plate, except for the
aprons of hotspot volcanoes and Pacific Bottom Water drifts along the southern
Kermadec Trench. Peter Lonsdale