Seismic stratigraphy od Santorini's Caldera: a contribution to the understanding of the Minoan eruption. Sakellariou D.

SEISMIC STRATIGRAPHY OF SANTORINI’S CALDERA: A CONTRIBUTION TO THE

UNDERSTANDING OF THE MINOAN ERUPTION

Sakellariou D.1, Rousakis G.1, Sigurdsson H.2, Nomikou P.3, Katsenis I.4, Croff Bell K.L.2, Carey S.2

1 Inst. Oceanography, Hellenic Centre for Marine Research2 Graduate School of Oceanography, University of Rhode Island, USA

3 Geology Dptm , National Kapodistrian University of Athens, Ilissia, Greece, 4 Geology Dptm., University of Patras

10ο Πανελλήνιο Συμπόσιο Ωκεανογραφίας & Αλιείας7-11 Μαϊου 2012, Αθήνα

HCMR surveys in the Caldera

Multibeam bathymetry 2001, 2006, 2012

Airgun 10ci seismic profiling 2006 & 2012

Chirp & 3.5kHz subbottom profiling 2012

Side scan sonar imaging 2012

Submersible Thetis dives 2006

ROV Max Rover dives 2012

Seafloor sampling 2006, 2012

North B

asin

South Basin

West Basin

Cape RivaCaldera

HCMR surveys in the Caldera

Multibeam bathymetry 2001, 2006, 2012

Airgun 10ci seismic profiling 2006 & 2012

Chirp & 3.5kHz subbottom profiling 2012

Side scan sonar imaging 2012

Submersible Thetis dives 2006

ROV Max Rover dives 2012

Seafloor sampling 2006, 2012

Pre-eruption relief

Air fall Tephra

Pyroclastic flows, surges

Lahars and pyroclastic flows

Minoan eruption deposits onshore

Minoan eruption Phase 1:Coarse grain air-fall tephra layer

Thickness: 10-11m max

Morphology of the submarine volcanic flanksYoung, upper slopes: steep, irregular

Old, lower slopes: gently sloping, smooth

Airgun 10ci profile 90-91

NORTH BASIN

Seismic stratigraphy of Santorini Caldera

NORTH BASIN

Seismic stratigraphy of Santorini Caldera

Airgun 10ci profile 39-38

NORTH BASIN

Seismic stratigraphy of Santorini Caldera

Airgun 10ci profile 40-41

NORTH BASIN

Seismic stratigraphy of Santorini Caldera

Deep Tow CHIRP profile 40-41

NORTH BASIN

Seismic stratigraphy of Santorini Caldera

Airgun 10ci profile 43-42

WEST BASIN

Seismic stratigraphy of Santorini Caldera

Airgun 10ci profile 87-88

SOUTH BASIN

Seismic stratigraphy of Santorini Caldera

Airgun 10ci profile 88-89

SOUTH BASIN

Seismic stratigraphy of Santorini Caldera

Airgun 10ci profile 47-48

SOUTH BASIN

Seismic stratigraphy of Santorini Caldera

Airgun 10ci profile 51-50-49-48

SOUTH BASIN

Seismic stratigraphy of Santorini Caldera

Airgun 10ci profile 49-48

Kameni lavas

Floating pumice

PyroclasticsPyroclastics

Pre-Minoan

Pre-Minoan

Air-fall tephra

slide

Interpretation of the seismic stratigraphy of Santorini’s Caldera

Cape Riva CalderaEruption took place outside the Santorini Caldera.Cape Riva pyroclastics flew into the caldera through the northern corridor.

Structural evolution of Santorini’s Caldera

(i) the thickness of the Minoan deposits on the caldera seafloor exceeds 100 m locally,

(ii) post Minoan deposits are negligible,

(iii) the lower, gently sloping parts of the slopes around Kameni islands are of Minoan age,

(iv) all three subbasins of the caldera existed prior to the Minoan eruption and were filled with pyroclastics during and after the 17th cent. BC eruption

(v) the Minoan eruption center was located where the present day Kameni islands are.

RESULTS

EUROFLEETSCaldera 2012 – July 2012

Girona University - HCMR - IPGP - WHOI

Autonomous Underwater Vehicle “Girona 500”

Payload: multibeam, sidescan sonar, camera, mass spectrometer

Deliverables: microbathymetry, morphology, photomosaic, geochemical mapping

1.00E-11

1.00E-10

1.00E-09

1.00E-08

1.00E-07

1.00E-06

10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46

mass-to-charge ratio

ion

pea

k in

ten

sity

(T

orr

)

ambient vent

CO

H2S

CO2

CH4

Hydrocarbon?

NOx

Mapping gas concentration in real time with the TETHYS mass spectrometer,

mounted on THETIS submersible

EUROFLEETSCaldera 2012

January 2012ROV Max Rover diveNorth of Nea Kameni380m depth

Small crater on the Caldera’s seafloor

EUROFLEETSCaldera 2012

THANK YOU

santorini.hcmr.gr