on 31 July 2016
This book was first published in 1976 (1993) 2003, has 361 pages, 11 chapters, 64 B/W photos and diagrams, and 22 B/W maps. The book is dedicated to author's cat -'Jeffrey'. This book tries to answer some common questions about volcanoes - What is a volcano - Why does volcanism exist - Are eruptions predictable - How dangerous or beneficial are they ? As we now know more of geology of Earth and Moon, we can understand volcanoes more closely. Volcanoes are known for their dormant status, eruption clouds, hot ashes, liquid rock ooze and tsunamis.
Most volcanoes are within 200km of the sea. Recently, active volcanoes means, active within the last 10,000 years. Earth's inner core is mass of iron and nickel, surrounded by dark rock of iron and magnesium, topped by very thin crust. The distribution of volcanoes resembles the distribution of Earthquakes. Any movement in the 6 large and many small tectonic plates can lead to earthquakes, above or beneath them. Meeting of plates leads to high level of seismic activity and volcanism. The large African Rift Valley volcanoes are of basalt alkaline ie Oldonyo Lengai (Mountain of God - produces washing soda (sodium bicarbonate).
'Ash-Flow' and 'Mud-Flow' from volcanoes causes destruction of life and property. Examples are :- Mt Vesuvius AD 79, Krakatoa 1883 and Mt Pelee 1902. The hot gas had killed many instantaneously, with no time to escape. Eruptions can be central, fissure, summit, flank, lateral or parasitic. It is when the high pressure gases escape, that liquid lava is sprayed high into the air, producing lava fountains. Under water eruptions are explosive, when red-hot magma comes in contact with large amount of sea-water forming instant steam.
Oxygen and silicon are the main elements of all rocks in the Earth's crust and make up of 99% of volcanic rocks, which can be dark or light. Emerging from the ground, the basalt lava is of the temp of 1,100'C. The 'aa' ;ava flow moves slowly on its track and can also form tunnels. Lava, without breaking the surface, can form a hill, where there was no hill before. Pyroclastic flow deposits (Tephra) can bury houses. Pyroclastic mud flows (Lahars - Indonesian word) can be fast and lethal. Steep slopes on volcanoes can lead to 'Hot Avalanches'.
The very hot pyroclastic gas flow is fast, noiseless and deadly. Volcanoes may form quickly or very slowly. their erosion can be slow or fast, destroyed by eruption or explosion. Craters are formed by eruption, explosion or subsidence (Caldera - Spanish for kettle). Erosion is caused by water, wind and ice. For a volcano to erode into a low hill, can take 15 to 20 million years. The neck or feeder pipe remain in the centre as massive pillars of rock (as seen in westerns). The side-effects of volcanoes are - earthquakes and tsunamis, dust in the air may cause strange colours of light around the Sun and the Moon (dust Veil).
Advantages of volcanoes are of course - digging Gold, silver, iron, copper, thermal heat, water and geothermal power. Volcano watchers study the significant changes and warning signs in the state of a volcano - to prevent loss of life and property from any future eruptions. Can barriers be built infront of the lava flows to divert them to unpopulated area ? A meteorite can also trigger a volcanic phenomenon, as seen on the surface of the Moon. Olympus Mons (Nix Olympica) is the largest volcano on Mars and in the Solar system. (27km in Ht, 500km in diameter, the crater is 100km in diameter containing 6 caldera).
Since this book was published, there has been more volcano eruptions, earthquakes and tsunamis, and we have more upto date pictures of these and other planets by the visiting crafts.
Some other books on Volcanoes are:-
(1) Volcanoes, MacDonald 1972
(2) Volcanoes, A Schreiber 2008
(3) Volcanoes, S Turnbull 2007
(4) 100 Facts of Volcanoes, C Oxlade 2009
(5) Walking The Giant, B McGuire 2013
(6) Island of Fire, A Witze 2014
(7) Volcano Discoveries, T Pfeiffer 2015
(8) Eruption, A Ganeri 2015
(9) Volcanoes, C Parker 2016
(10)Volcanoes and Earthquakes, J Bundle 2016
Having born in Kenya and seen many of the Great Rift Valley volcanoes, I enjoyed reading this book.