1. 13.Air fall ash and tuff Dan Barker, March 2009 SW Izu Oshima, Japan

2. Pyroclastic material that free-falls from an eruption cloud as individual particles is airfall. Much is ash ( < 2 mm), but larger pieces of low-density pumice also can fall from vigorously convecting clouds. If an airfall deposit escapes rapid erosion, mostly by becoming buried, it may become indurated. Indurated deposits cannot be excavated by a shovel or trowel; they are now rocks. Ash becomes tuff and lapilli become lapilli tuff.

3. Airfall ash decorates this Mercedes during a 1983 eruption of Etna. Catania, Sicily.

4. This convecting plume above a grain field fire in SE Idaho is analogous to an ashy cloud from a volcano.

5. The mushroom cloud on the horizon is an eruption plume from White Island, New Zealand.

6. Ash plume from partial dome collapse, Mt St Helens, May 20, 2006.

7. Erosion is removing this unindurated airfall in the foreground. Fogo, Cape Verdes.

8. Airfall from the 1886 eruption of Tarawera, New Zealand, still covers this forest floor.

9. The black 1065 AD airfall from Sunset Crater, AZ apparently caused abandoning of the Wukoki settlement nearby.

10. The basal part of this 3400-yr-old airfall in New Zealand has pumice lapilli and charred wood.

11. The road cut in the preceding slide shows 4 carbon-dated airfalls separated by buried soils.

12. May 18, 1980 airfall at Mount St Helens. Some of this is fresh pumice and the rest is fragments of older rocks from the volcano.

13. The May 18, 1980 airfall killed many of these trees by stripping off bark, branches and needles.

14. More airfalls and paleosols, North Island, New Zealand

15. Airfalls drape over any pre-existing topography. E of M. Francelho, Brava, Cape Verdes.

16. This road cut in SW Izu Oshima shows draping over topography, and unconformities recording erosion between airfalls.

17. This is a more dramatic unconformity in the road cut

18. Airfall and a few impact sags, Isabela I, Galapagos

19. Lapilli tuff of tuff ring, Ranu Raraka, Rapa Nui

20. A closeup of the lapilli tuff. This is the rock from which the Easter Islanders carved their giant stone figures.

21. Airfall, El Cajete pumice, Valles caldera,NM

22. Altered ash layers in Cretaceous limestone, McKinney Falls State Park, TX. G. Byerly for scale.

23. Finally, some controversy. This is a broken column from the Roman villa at Oplontis, buried in 79 AD by Vesuvius. Archeologists say that the column collapsed during an earthquake more than 10 years earlier. Then why is the column part on the right resting on airfall? Most likely the weight of airfall on the roof collapsed the column in 79 AD.