Hawaiian Submarine Volcanism. Stages of Hawaiian Volcanoes:

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1 Hawaiian Submarine Volcanism November 1, 2011 Mary Tardona GG 711 Stages of Hawaiian Volcanoes: Typically, three main stages: Pre shield Shield Post shield Sometimes followed by: Rejuvenation Stage GG 711, Fall 2011, Lect. 11, Mary Tardona 1

2 Classification Na2O + K2O wt% Alk-SiO2 6 Basanite 5.5 Hawaiite Alkali Basalt Basaltic Andesite Tholeiitic Basalt SiO2 wt % LeBas LeBas Macdonald Macdonald J2-380_XRF J2-381_XRF J2-551_XRF J2-556_XRF J2-557_XRF J2-560_XRF J2-380_glass J2-381_glass J2-556_glass J2-557_glass Submarine Alkalic Lava Lower T Low Volume Loihi ~1,700 km 3 Kilauea ~3,350 km 3 Pre shield GG 711, Fall 2011, Lect. 11, Mary Tardona 2

3 Shield Building Submarine Subaerial Tholeiitic Higher T High eruption rate Highest Volume >95% Kilauea Alkalic Cap Post shield Low T Lower eruption rate Slightly more explosive Higher viscosity Lava contains slightly more gas More crystal rich GG 711, Fall 2011, Lect. 11, Mary Tardona 3

4 Rejuvenation Stage 500,000 3 million years after main eruption Not continuous, can have gaps of up to 1,000 years between eruptions More explosive alkali SiO2 LeBas 6 LeBas Basanite 5.5 Monogenetic Hawaiite Low Volume Highly alkalic lavas Na2O + K2O SiO2 wt % Macdonald Macdonald J2-380_XRF J2-381_XRF J2-551_XRF J2-556_XRF J2-557_XRF J2-560_XRF J2-380_glass J2-381_glass J2-556_glass J2-557_glass Rejuvenation Stage Honolulu Volcanics East Maui Volcano GG 711, Fall 2011, Lect. 11, Mary Tardona 4

5 Preshield Shield Building Postshield Alkalic Tholeiitic Alkalic Na2O+K2O Waianae Volcano Alk-SiO2 Lualualei Kamaileunu Palehua labas MacDonald Diamond Head SiO2 wt % GG 711, Fall 2011, Lect. 11, Mary Tardona 5

6 Hawaiian Submarine Volcanism Early Stages Rift Zone Submarine rejuvenation Loihi Preshield and Early Shield Stage Submarine Hawaiian Volcanism Transitionaltholeiitic lavas 1996 eruption Shallow earthquakes Few 0 5 km mostly around 8 km GG 711, Fall 2011, Lect. 11, Mary Tardona 6

7 Preshield and Early Shield Stage Submarine Hawaiian Volcanism Loihi 1996 eruption Pele s pit Collapsed location of great hydrothermal activity 600m diameter Bottom 300m below original surface Exposed massive columnar jointed lavas Preshield and Early Shield Stage Submarine Hawaiian Volcanism Loihi 1996 eruption Intense hydrothermal plumes C anomalies up to 8km away *MOR eruptions typically have ~ C anomalies (though few have been recorded as higher) GG 711, Fall 2011, Lect. 11, Mary Tardona 7

8 Preshield and Early Shield Stage Submarine Hawaiian Volcanism Loihi 1996 eruption Vent fields Temperatures up to 77 C Diffuse venting although 13 m wide fissures venting large volumes of water in the south rift vent area High Temp sulfide minerals found Indicate vent waters at temperatures of 250 C Loihi Preshield and Early Shield Stage Submarine Hawaiian Volcanism 1996 eruption Dense lava Pillows Sheet flow Pele s hair Limu o Pele M.Garcia *Figures and Loihi data taken from SOEST s Hawaii s Center for Volcanology Website GG 711, Fall 2011, Lect. 11, Mary Tardona 8

9 Rift Zone Volcanism : Puna Ridge Tholeiites Flow fields Sheet flows Lobate flows Pillow flows Distinguished from lobate flows by extrusion marks on surfaces Found at all depths along the ridge Rift Zone Volcanism : Puna Ridge Pillow Ridges Pillow flows along fissures Up to 500 m to a few km long, few tens of meters wide Located at the shallow end of Puna Ridge (up to <2000m) GG 711, Fall 2011, Lect. 11, Mary Tardona 9

10 Rift Zone Volcanism : Puna Ridge Cones Largest cones (heights >100m) have flat tops and craters Flanks covered in rubble and hyaloclastites Possibly indicative of phreomagmatic eruption Deep craters Draining of magma after eruption ceased Columnar jointed lavas Indicate cooling of meters thick flows (Smith et al., figure 6) Smaller cones Height <100m Pointed tops Elongate and tubular pillows on flanks Rift Zone Volcanism : Puna Ridge Terraces Near circular, flat topped, Several km wide, few hundred meters high High Volume km 3 Two Main types: Slightly domed tops Inflation features Terraces with at least one summit crater Possibly tube fed *Lister and Dellar Formulation* Skylights Happens on the slow spreading Mid Atlantic Ridge Possibly Dike fed GG 711, Fall 2011, Lect. 11, Mary Tardona 10

11 Rift Zone Volcanism : Puna Ridge Stair Stepping Terraces ( m) Increase in volume down rift A down rift terrace down has radiating tube network from crater Lava flowed out onto horizontal summit from the crater Numerous craters and collapse features Deep step terraces ( m) Pillow, Lobate, and sheet flow cover Rift Zone Volcanism : Puna Ridge Two main trends in morphology vs. depth Two fissures on crest of ridge Only at shallow depths above 1100m Cones at depths of ~600 ~2200m GG 711, Fall 2011, Lect. 11, Mary Tardona 11

12 Submarine Rejuvenate Volcanism Alkalic Cones Pillow lava Base (~890m) Near top of one cone (~430m) Talus like blocky lavas at summit (~500m) Effusive eruptions of higher viscosity lavas Vesicle and crystal rich Submarine Rejuvenate Volcanism Cones Shallower cones (~ m) Fine bedded/cross bedded ash deposits Fine grained ash Volcanic breccia Grain size increasing toward top of cones Surtseyan style, explosive eruption Surtsey, NOAA 1963 GG 711, Fall 2011, Lect. 11, Mary Tardona 12

13 Submarine Rejuvenate Volcanism Flank of Diamond Head: From 562m to 494m deep Submarine Rejuvenate Volcanism Up the flank of Diamond Head Finely layered volcaniclastic deposits (panel c) Volcaniclastic sediments draped over pillows (panel d) GG 711, Fall 2011, Lect. 11, Mary Tardona 13

14 Hawaiian submarine volcanics are dynamic Early Shield stage Pillow flows Sheet flow Pele s hair Limu o Pele Pit craters Ridge Pillow flows Lobate flows Fissures and effusive flows Cones Terraces craters Lava tubes Rejuvenations Pillow flows Volcaniclastics Cones GG 711, Fall 2011, Lect. 11, Mary Tardona 14