• Dynamic types related to magma/water interactions

• Dynamic types related to dissolved bubbles

• Dynamic types related to domes growth and collapse

• Dynamic types related to lava flows etc.• Complex edifices• Destruction of volcanic edifices

Figure 4-2. Volcanic landforms associated with a central vent (all at same scale).

Shield Volcano: Mauna Loa, HI

sea level

0 10 km

scale

Composite Volcano:

Mt. Rainier, WA.

Cinder Cone:

Sunset Crater, AZ

a

b c

Dome:

Lassen Peak, CA

d

vent

Réunion island

Réunion Island

Piton des Neiges (3100 m)(extinct)

Piton de la Fournaise (2600 m)(active)

Lava flows and more lava flows…

But note also the grey material at the bottom…

Helicopter view, NW coast (btw, this cliff tends to collapse quite often on the road. Last time was last

week…)

Cones groupe in Réunion + flows

Shield volcano

• Mostly a pile of basaltic flows!

• Strombolian & Hawaian

Strato-volcanoes

Figure 4-3. a. Illustrative cross section of a stratovolcano. After Macdonald (1972), Volcanoes. Prentice-Hall, Inc., Englewood Cliffs, N. J., 1-150. b. Deeply glaciated north wall of Mt. Rainier, WA, a stratovolcano, showing layers of pyroclastics and lava flows. © John Winter and Prentice Hall.

Lava flows…

(Here, in the caldera wall on the top of Mt Pelée)

… and explosive phases

And erosion.

Shield volcanoes vs. stratovolcanoes

Shield volcanoes• Basaltic• Intraplate (hotspot)• Relatively flat• Effusive (lava flows,

strombolian cones)• Minor explosive

events (phreatic)• Erosion and flank

collapse

Stratovolcanoes• Andesitic to dacitic• Subduction• Rather steep• Explosive

(plinian/pelean)• Minor andesitic flows

a• Erosion, lahars and

flank collapse

• Dynamic types related to magma/water interactions

• Dynamic types related to dissolved bubbles

• Dynamic types related to domes growth and collapse

• Dynamic types related to lava flows etc.• Complex edifices• Destruction of volcanic edifices

Erosion and rivers

Successive valleys and valley fills(Réunion Isl.)

Lahars

« Normal » landslides

Cilaos

Major landslides?

Major debris avalanches forming the populated plateaux…

Successive avalanches in the core of the volcano

Consolidated breccias

Megabreccias

(Well, Ok, not in Réunion isl…Sorry, did not find photos from there)

Superposition of breccia and flows!

.. And more breccias

Evidence for successive events: Breccia cut by dykes

.. How major?

Piton de la Fournaise

Rift zone = major sliding plane?

Evolution by successive flank collapses?

A new view on shield volcanoes:

• A succession of lava flows, and erosion– Local erosion (lahar, valleys)– Local/big erosions (large landslides, big

depressions)– Major landslides (flank collapse), might be

associated with eruptions (as in MSH, but no hard evidence for that)

Volcanic islands:

Tropical paradises or heaps of rubble?