Goh Cheng Leong: Chapter 3 YouTube Lecture Handouts Geography
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Goh Cheng Leong Chapter 3: Vulcanism and Earthquakes (Physical and Human Geography)
Certificate Physical & Human Geography Goh Cheng Leong
Chapter 3: Vulcanism and Earthquakes
Volcano
Intrusive Landforms
- Laccolith
- Lopolith
- Phacolith
- Batholith
- Sills
- Dykes
Origin
- Vulcan – God of Underworld – furnace below Volcano in Sicily
- At zones of weakness – fold or fault
- Temperature increase for for 65 feet
- Magma has gases - Sulphur, Nitrogen , Chlorine – through the vent or opening
Types of Lava
- Acidic – light colored, highly viscous, flow slowly, steep-sided, pyroclasts, bombs, spine or plug form crater as Mt. Pelee (Martinique) , plug remains in Puy de Dome, France
- Basic – hottest, highly fluid, Fe & Mg, lack silica, dark color, highly fluid, flow quietly, thin sheets and spread over large area – shield or dome
Types of Volcano
- Active - Kilauea
- Dormant - Mauna Kea
- Extinct - Kohala
Extrusive Landforms
- Lava Plains and Basalt Plateaux – fluid – Snake basin, USA; Deccan; Iceland
- Lava domes or shield volcanoes – volcanic cones – Mauna Loa & Kilauea (caldera with active vent pours forming lava pit of Halemaumau)
- Ash & cinder cones – less fluid – large crater & steep slope – small volcano in groups – Mt. Nuovo (Naples) & Mt. Paricutin (Mexico)
- Lava tongues & lava dammed lakes – confined in valleys
- Lava bridges
- Lava tunnels
- Volcanic dust – fine particles
- Dust and Ash – black snow
- Pyroclast – coarse fragments – cinders/lapilli, scoria, pumice and volcanic bombs
Composite Cones
- Highest and most common
- Called Stratocones – main conduit and subsidiary dykes and pipes
- Mt. Etna (Sicily, Italy)
- Mt. Stromboli (Lighthouse of Mediterranean)
- Mt. Vesuvius
- Mt. Fiji
- Mt. Popacatapetl
- Mt. Chimborazo
Mt. Vesuvius
- Bay of naples – erupted 79 AD
- Parasitic cone
- White hot lava
- Cauliflower form – pyroclasts & ashes
- City of Pompeii – buried beneath 25 feet of ashes
- City of Herculaneum – mudflow – 50 feet thick
- In 1631 – avalanche with red hot debris – ruined 15 towns and killed 4,000, 1 foot thick ashes in Naples
Mt. Krakatau
- August 1883
- B/w Java & Sumatra
- Dense black cloud – 20 - 50 miles high
- 2⟋3rd island collapsed
- Caldera formed
- Explosion heard 3000 miles away
- 36,000 people drowned in coastal areas
- Erupted again in 1927 – pushed cinder cone from submarine floor of 220 ft ASL by 1952
- Anak Krakatau or Child of Mt. Krakatau formed
Mt. Pelee
- West Indies
- Erupted in 1902
- White hot lava
- Superheated stream
- Nuee ardente (glowing avalanche)
- 30,000 except 2 killed in . Pierre (capital of Martinique)
- Spine formed by pasty lava- solidified
Distribution of Volcanoes
- Circum-Pacific ring of fire or Pacific ring of fire – 2⟋3rd volcanoes
- 100 active volcano in Philippines, 40 in Andes, 35 in Japan, 70 in Indonesia
- Pacific coast – more active (Aleutian, Java, Sumatra, Kamchatka, Solomon, New Hebrides)
- Atlantic coast – less active (Madeira, Ascension, Helena, Cape Verde, Canary)
- Iceland & Azores – active
- Mediterranean – associated with Alpine folds (Vesuvius, Etna, Stromboli, Volcano)
- Himalayas – no active volcanoes
- Africa – East African Rift valley – active (Cameroon) , extinct (Kilimanjaro and Kenya)
Geyser & Hot Springs
- Geyser – fountain of hot water – Iceland, Rotorua (N. Island, New Zealand) , Yellowstone National Park (USA) – Old Faithful erupts every 63 minutes
- Hot Springs – dissolved minerals – Iceland, Hawaii, Japan
Earthquakes
- 50,000 tremors per year
- Minor – vibrations
- Major – faults
- Tidal waves – tsunamis
- Fire
- Building collapse
- Fissures open- surface waves
- Infrastructure affected
- Measured seismograph
Major Earthquakes
- 1755: Great Libson (Atlantic west) – tidal waves – 60,000 died
- 1923: Tokyo & Yokohama –
- 1906: San Francisco
- 1920: Kansu, China – 2 lakh died & 1 lakh cave dwellers in 1927 affected
- 1960: Agadir, Morocco: 10,000 died
- 1968: Kakh, E. Iran
Distribution of Earthquakes
- Coincides with volcanoes
- 70%: Circum-Pacific belt
- 20%: Mediterranean-Himalayan belt
✍ Manishika