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Types of volcanic activities Chapter 5, pages 113-131 On-line text (

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1 Types of volcanic activities Chapter 5, pages 113-131 On-line text (

2 Hawaiian activity (pages 114-117) Example: you guessed it! High temperature and low viscosity basaltic lava flowsHigh temperature and low viscosity basaltic lava flows Low proportion of dissolved gasesLow proportion of dissolved gases Fire fountains and lava lakes are typicalFire fountains and lava lakes are typical Mildest form of volcanic activityMildest form of volcanic activity

3 Kilauea eruption, 1955 MbQY&feature=related Kilauea today Examples of Hawai’ian activity

4 Strombolian activity (pages 117-129) Example: Stromboli, Etna Intermittent, discrete explosive bursts Pyroclasts and lava fragments are ejected with loud bangs Basaltic magma is involved, but with higher viscosity than Hawaiian magma NO eruption column develops Noisier than Hawaiian eruptions, but still relatively harmless

5 Stromboli eruption, 1998-2000 o/index-en.html Etna eruption, 1999 o-en.html Examples of Strombolian activity

6 Vulcanian activity (pages 120-123) Example: Vulcano, Italy Smaller magnitude of eruptions Eruption columns are MUCH higher than Strombolian eruptions (up to 10-20 km high) More violent and explosive than Strombolian eruptions High viscosity, usually andesitic magmas are involved Growing lava domes, ash fall and pyroclastic flows are common Volcanic effects are not widespread


8 Sub-plinian or Vesuvian activity (pages 123 - 124) Example: Vesuvius Higher eruption columns than vulcanian eruptions (nearly 30 km high) Eruption columns are sustained for longer periods Extensive tephra and ash deposits More silicic magmas are usually involved Follows eruptive cycles of 25-30 years

9 Plinian activity (pages 124 - 125) Examples: Vesuvius, year 79, Pinatubo, 1991 Eruptions that make history Powerful eruptions with exit velocities of several hundred meters per second. Eruption columns can reach up to 45 km (reach the stratosphere) Widespread tephra and ash deposits Involves mostly silicic magma

10 Ultraplinian activity (page 125) Example: Taupo eruption, New Zealand, year 181 None in the recent historic past… thank goodness The Taupo eruption created 10 cm thick Tephra deposits which covered more than 15,000 square kilometers Eruption columns must be higher than 45 km

11 Peléean activity (pages 125-126) Example: 1902 eruption of Mt. Pelée Characteristic feature: nuées ardentes (also known as GLOWING CLOUDS or pyroclastic flows or Pyroclastic Density Clouds, AKA PDC) ture=related ture=related Can be associated with Vulcanian or Plinian eruptions Note: The same volcano can show several different types of activities even during the same eruption

12 Hydrovolcanic eruptions (pages 126-131) where volcanoes meet water Movie clip: Brimstone Pit eruption, 2006, Mariana volcanic chain, at a depth of 555 meters. Happens when volcanoes erupt on the ocean floor, under a lake, below glaciers etc. Or when volcanic vents on land encounter surface water (phreatic water) in an aquifer or wet sediments

13 When water comes in contact with hot volcanic ROCKS (NOT magma), violent steam explosions can happen. This is known as PHREATIC ERUPTION (page 126) When large amounts of surface water interacts with magma, PHREATOMAGMATIC eruptions occur (page 126) First, the magma becomes chilled and develops a solid skin, which then becomes fragmented These eruptions are violently explosive, comparable to nuclear reactor meltdowns

14 Hydrovolcanic eruptions Surtseyan (page 127) Strombolian eruption + water Powerful blasts of fragments with steam plumes May form volcanic islands (e.g. Surtsey, Iceland) Phreatoplinian (page 130) Sub-plinian or plinian eruption +water None has been observed, but old deposits exist in New Zealand

15 Submarine volcanoes (chapter 14)

16 Eruption in shallow water Basaltic eruption –when basaltic lava reaches ocean (e.g. Hawaii) –FLUID lava becomes chilled –Steam forming at the contact prevents large explosions –Seawater reacts with lava to form hydrochloric acid (lava haze or LAZE) –Underwater basaltic eruption forms PILLOW LAVA (pages 356-357)PILLOW LAVA –Surtseyan type eruptions can happen Silicic eruptions –Relatively rare –explosive –Can be phreatomagmatic –Can form important economic ore deposits (page 359)

17 Eruption in deep water Visible example: Afar depression, EthiopiaAfar depression, Ethiopia Basaltic eruption mostly –Along mid-ocean ridges and submarine hotspots –Pillow lava common but strombolian type eruptions can happen (lava fountains under water) –Seawater reacts with hot rocks and magma to create hot water rich with metallic sulfides –Such hydrothermal activity (more on that later) produces BLACK (also WHITE) SMOKERS (pages 362-363) –Ecosystem based on CHEMOSYNTHESIS

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