Alvin Dive 3348
7 February, 1999
Pilot in Training: Bruce Strickrott (with Blee Williams)
Port Observer: John Sinton
Launch Position: 18° 31.54'S 113° 25.03'W
Time Depth Hdg
~0800 Alvin in the water
0906 Setting up to do maggie spins in water column; 1 deg/sec, spinning counter clockwise.
0924 Finished spinning
0944 2582 About 20 meters off bottom.
0945 2597 130 Bottom visible in SIT camera, looks like slightly elongated pillow lavas; fairly heavily sedimented. Bottom now in sight with some clear pockets of sediment between lava forms; some of these pockets are connected. Probably about 5 m off bottom.
0947 2599 130 Bottom clearly in sight. Pillow lavas with buds with definite sediment pockets between them. Some pillows are broken. Mixture of elongate pillows, some flatter, more lobate pillows and some quite bulbous pillows all present here.
0952 2600 Looking for place to sample. Age about 2.0. Good buds.
0957 Still looking. Striated pillows, locally elongated with buds and horns at least 15 cm long, locally more. Surface not very glassy. Some digital still pictures taken of budded, elongated pillows on starboard side.
1000 2598 Sample #1: pillow bud, broken on both ends, about 15-20 cm long, about 7-8 cm in diameter.
1005 Window temp = 1.5 1.7°
1007 External camera set on 15 sec rep rate.
1009 2598 119 Starting to go uphill
1010 2598 124 Many isolated sediment ponds, not particularly connected. Pillows are very well striated here. Good buds, mainly about 15 cm long, but some up to abut 30 cm. Some sediment ponds almost connected in some places. About 1 m of relief on pillows. Typical pillow diameter about 1 m.
1013 2591 122 Some very elongate pillows coming down from 10 o'clock as we move upslope obliquely. Pillows becoming more lobate and sediment pockets becoming more connected. Age = 2.5. Anemones
1014 2588 123 Heavily sedimented lobate lavas. Local relief < 1 m. There are some pillows here also and in at least one case the pillows overlie lobate lavas.
1016 2581 122 Elongate pillow flow with relief of about 1 m. Sediment thickness may have decreased. This flow is heavily budded.
1017 2579 122 Looks younger than where we landed. Still coming up slope.
1019 2574 124 Possibly leaving heavily budded flow, but still in pillow lava. Still coming up slope. One fissure running about 230 out sbd side.
1022 2569 124 Coming over a slight depression that steps down about 1.5 meters. Also beginning to see some cracks striking about 9:30 to the 310°. Some big pillows about 2-3 m acoss. Seem to be reaching the crest of the hill. Some lobate lavas and less buds than earlier.
1024 2566 120 About 1 m off bottom. Big drop off in front of us to SE. Looking for a place to sample.
1058 2569 Sample #2: 20-25 cm-long pillow bud.
1059 107 Just moving out over scarp which runs about 015-020° here. Mesotech shows down to the right. Mesotech indicates first scarp is about 18-20 m high.
1102 2566 Bottom at least 20 m below us.
1105 2583 120 Bottom still at least 4 m below us. Another drop off ahead of us.
1106 2589 120 Another drop off here. Heavily sedimented pillow lava.
1108 2593 122 Just starting to go over the next drop off. Lobate lavas with some cracks. Bearing of scarp is almost due north here.
1109 2592 122 Just coming over scarp
1110 2608 040 Turning to 120. Can see bottom in SIT camera. Wall is broken pillow lava. Quite a bit of talus and some very large pillows.
120 The step down was part of a subsidiary graben as we then started coming back up again. Mostly lobate lava here. Step up at least 2, maybe 3 m.
1116 2608 120 Steps down about 1-1.5 m with rubbly in the bottom of it, and then into lobate lava. Many small cracks of only 20-30 cm in width running through here. Many lobate lavas and some pillows here are nearly in tact. Another drop off ahead of us.
1117 120 Moving out over scarp.
1118 2607 Bottom of scarp about 12 m below us. Turning to 040. Truncated pillow and lobate lavas in scarp.
1121 2621 006 In rubble pile near base of the fault.
1122 2619 036 Turning to 120. Large boulders several meters across at base of fault. More steps down in front of us.
1124 2619 123 Coming back up a little. Many broken lobate and pillow lavas. Fissures running about 010°. Highly broken up lavas.
1125 2615 123 Came out over a 2-3 m scarp stepping down. Lobate lava, fairly heavily sedimented. Probably are nearing the east wall as I can see talus out in front of us.
2607 All talus as we start to move up east wall. Turning to 230°. No younger lava apparent on this crossing of the graben.
1129 2605 220 Descending east wall.
1131 2616 234 Shattered lobate lavas, very broken up and tectonized. Not all that much sediment here. Window temp here = 1.9°.
1135 2619 211 Setting down to get CTFM reading.
1142 2618 210 CTFM indicates we are close to the east wall.
1152 2618 170 Sample #3. Piece of broken lobate lava from graben floor. Looks like Mn coating on lower surface. Piece about 25-30 cm across and about 10 cm thick.
1153 2618 Finished sampling graben floor. Turning to 200
1159 2617 190 Broken lobate and pillow lavas all around us.
1206 2617 226 Following graben floor with broken lobate lavas on floor.
1207 2618 202 Broken lobate lava with quite a bit of sediment on it.
1208 2618 200 Here have rubble on both sides. Slope going up to port side.
1209 2617 198 Axis of deep just below us. We have been following a small deep about 15 m wide that strikes about 194° here. Serious talus on port side. Deepest part turns slightly to SW to abut 220°.
1212 2617 219 Navigating down center of the graben using the CTFM.
1214 2617 220 Can see thin flows exposed in cross section in a scarp on the stbd side (west wall) that also have lobate lavas here. Some lobate lavas are nearly hollow and uncollapsed. Lots of talus at base of wall. Graben width is no more than 50 m here. Broken lava forms and talus here.
1218 2612 186 Riding along the graben center (axis of the deepest part)
1219 2613 202 Pretty much in the center of the graben. We just moved away from some talus on the port side. Some large pillow fragments in the talus. CTFM inicates we are in the center of a 50 m-wide graben. Bottom is flattening out below us.
1221 2614 202 Graben is widening here. Here close to east wall. All talus on the port side.
1224 2613 Contact with sheet flow coming up here. Have it on the Alvin video.
1227 2614 273 Just come onto a place where sheet lava is draping onto talus and broken lobate lava. Significant sediment accumulation on sheet flow. Moved the submarine up so that the basket is just even with the top surface of the sheet flow and mesotech indicates that the bottom is 4 m below us. Hence the moderately steep flow front is 4 m high. Will attempt to sample the sheet flow.
1233 2614 Sampling the sheet flow. Flow is a smooth sheet flow that is fairly flat.
1238 2614 Sample #4. Flat sheet from just above flow front at contact.
1242 267 Just getting ready to leave sample site. As we look west can see that the first graben wall is about 90 m away from us so this contact is right where the graben widens from about 50 m to more than 90 m.
1243 2613 250 Moving off over sheet flow.
1245 2612 Very flat sheet flow with cross flow cracks in it. Flow has longitudinal lineations. The flow is coming up in little steps. It looks like the flow is broken down in large slabs toward the flow front.
1247 2614 250 Intraflow contact between flat sheets and more folded, almost braided sheet flow. This next flow lobe steps up almost 3 m above the flat sheet flow surface. There are some depressions which look like subsidence pits in this part of the flow. Local flow direction looks like it is nearly out of the west here. Can also see a fairly clear fissure here which has broken sheet flow on its walls.
1251 2610 246 Stepped up 3-4 m. This step is up onto lobate lavas, but there is still sheet flow around. Sheet flow flow direction here is down from about 130°. This flow appears to be at least slightly tectonized. Mainly gently folded to lineated sheet lava here.
1253 2610 253 Sheet flow is becoming jumbled sheets with some folded sheets near a contact with broken lobate lavas.
1255 2608 Near some sort of contact, probably near west wall.
1307 2611 Moved back away from west wall. Here have folded to jumbled sheet flows and some much more massive lavas, gradational into lobate lava.
1346 190 Sample #5. Folded sheet flow. Sample taken about 20 m from the western wall of the graben.
1349 2608 183 Just beginning to move away from sample site. Lavas changing into lobate lavas. Fairly flat lavas with attached corals. One prominent fissure here strikes 190°.
1351 2609 189 Lobate lavas, fairly heavily sedimented, locally slightly broken. Sloping down to left (east). CTFM indicates the graben is 70-90 m wide here. We are more or less in the middle of it. Lobates are locally gradational to pillow lava. Some broken shells here.
1354 2609 204 Fissure running parallel to us here (204°). Also one on stbd side. These look like tectonic cracks. Can also see a lobe of sheet lava on top of the lobate lava.. This is folded sheet flow.
1356 2608 203 Now in flat sheet flows with a fissure striking off at about 180°. Flow has lineations or small folds that strike almost orthogonal to submarine here.
1357 2608 203 Moving into jumbled sheet flows.
1358 2607 203 Now into pillows and lobate lavas. Mostly fairly flat lobate lavas here, after coming through some more bulbous pillows. CTFM indicates we have been moving almost exactly down the center of the graben. We are slightly closer to the west wall moving obliquesly toward the east wall which is about 30 m away. Thus, the graben is very narrow here.
1359 2606 203 Back into more sheet flows, mostly somewhat folded and locally almost jumbled. Significant sediment on it.
1401 2603 CTFM indicates we are presently right in the middle of the graben, which is about 100 m wide here. Folded and jumbled sheet flows here.
1403 2603 Turning south to ~150. Sheet flows.
1404 2601 151 Climbing up slightly. Wall out in front of us about 40 m away. Folded to jumbled sheet flows here.
1405 2601 160 Folded and jumbled sheet flows. Fissure running on port side. Sheets give way to lobate lavas that are cut by a fissure that is about 6 m deep. Lobate lavas are elongate flowing down from right to left (from about 195 toward 015). Can see a large drop off coming up. Drops 5 or 6 meters down. Broken lobate lavas on walls of this slot as we approach the east wall.
1408 2595 155 Climbing up wall of broken lobate lava.
1410 2593 Came up east wall a ways.
1412 2590 214 Trying to move away from the eastern wall. There are large broken blocks on both sides.
1413 2590 216 As we leave the eastern wall we cross a large slot about 10 m deep between the surface of the flow and the eastern wall. This slot is something like 15-20 m across.
1414 2591 Lava here is broken lobate lava and some broad sheet-like material.
1417 2591 216 Crossed another small fissure. Mostly lobate almost transitional to sheet lava. Several clear fissures, up to 2 m wide. Many are open fissures but there are some with throw. One here steps up to our right (NW) by about 1 1.5 m.
1419 2591 215 Pillow lavas here having crossed a transition from lobate lavas. There is a lot of relief on these pillows, up to 2 m, and some definite fissures cutting through them. Then drops off 1-2 m along what is probably a fault scarp. CTFM says close to center of graben.
1422 2596 170 Going over a fissure is at least 3 m wide and more than 5-6 m deep cutting budded pillow flow.
1441 2595 Still sampling
1507 2596 Sample #6. Bud from pillow lava.
1516 2596 Heading off at 190. Very near center of graben.
1517 2592 191 Large number of fissures here cutting budded pillows. Fissures mainly strike about 170.
1518 2591 193 Parallel fissures up to 2 m wide but many are partially filled with rubble. Depth unknown. Beginning to see some flatter pillows transitional to lobate lavas. Fissures and cracks are closely spaced, every 10-15 m.
1519 2589 191 Lobate lavas here, some are collapsed. Look like they are less than 0.5 m thick. These are gradational to platy lobate lavas.
1520 2587 192 Now moved into jumbled sheet flow.
1521 2586 192 Fissure on port side running about 185. It is about 3-4 m wide with sheet flows on both sides. Looks very deep, at least 7 m. Surface is sheet flows but can see some more lobate lavas deeper in the walls of the gja. Fissure turns parallel to track at 192.
1523 2587 187 Folded sheets giving way to lobate and then elongate pillows flowing down from the right (west). Then into all budded pillows.
1524 2584 192 Bulbous, budded, striated pillows, with diameters of 1-2 m. although there are some lobate lavas here too, near edge of the open fissure.
1527 Down looking SIT cam looking into the fissure.
1531 2581 225 Looking for place to sample.
1539 2581 Sample #7. Bud from pillow lava, transitional to lobate.
1540 Weights away. As we rise off the bottom we see wall about 100 m to our west. Lost the wall as we got to an elevation of about 2567 m.