Geography Chap 3 (Goh Cheng Leong + NCERT)

Chapter 3

Volcanism and Earthquake

--Type of Landform depends on:
      >Fluidity & Strength of Magma + types of (cracks+faults+joints) that it penetrates + manner in which it escapes to surface.

--Solidification of Magma =Intrusive landform(called Plutonic rocks) +Extrusive landform(Volcanic rocks)
--Both Plutonic + Volcanic rocks = igneous rock.

Landforms of Igneous Intrusion:
--They come to surface after prolonged erosion unlike extrusive landforms--image  ↓(in next to next heading).


--Batholiths:
>Batholiths form the core of huge mountains and may be exposed on surface after erosion.
>These are granitic.
>Wicklow Mountain in Ireland.

--Laccoliths:
 > These are large dome-shaped intrusive bodies connected by a pipe-like conduit from below.
 > These are basically intrusive counterparts of an exposed domelike batholiths.
 > Karnataka plateau is spotted with dome hills of granite rocks. Most of these, now exfoliated, are examples of laccoliths or batholiths.

--Lapoliths :
 > develops into a saucer shape, concave to the sky .
 >Ex- Transval , South Africa.

--Phacolith :
 > wavy mass of intrusive rocks (syncline + Antisyncline).
 > wavy materials have a definite conduit to source beneath in the form of magma chambers (subsequently developed as batholiths).
 >Cordon Hill in England.

--Sills:
   > Horizontal intrusion.
   >Thin sheet || thick sills. Ex- Great Whin Sill of N.E. England.

--Dykes.
   > Vertical intrusion.
   >becoz of narrowness= seldom dominates landscape.
   >Can be upstanding wall of shallow trenches (depends on corrosion resistance to nearby rocks)
   >most commonly found intrusive forms in the western Maharashtra area. These are considered the feeders for the eruptions that led to the development of the Deccan traps.

Type of Lava:
--Basic Lava:
  > (Fe, Mg) > SiO2 (silica).
  >Property = Highly Fluid.
         >>as a result = spread to large area(as move fast before solidifies).
         >>forms thin layer over great distance.
>Appearance =Gentle slope + wide diameter + Flattened shield or dome.

--Acid Lava:
  > SiO2 > (Fe, Mg).
  >Property= Highly Viscous.
         >>as a result= spread less
         >>thick layer
  >distinct feature:
      >>Viscosity ↑ = speed ↓ è rapid Congealing.

      >>this Congealing sometimes = obstructs out flow.
      >>Result = Pyroclast AKA Volcanic Bomb.
>Appearance:
      >>sometime Lava solidies within conduit = forming Spine.
      >>some spine are very resistive = side by mountain erodes leaving= rising Spine between.
      >>Ex- Mt. Pelee in Martinique(Carabean island)

Type of Volcanos:
--Active = Barren Island, India.
--Dormant=Narcondom Island, India.
--Extinct= no one is sure when volcano goes extinct. Mt. Karataku, was thought to be extinct but it erupted.




Extusive landforms:
--Formed by Basic Lava:
   >Produces Extensive Lava Plains=Snake basin(USA).
   >or Produces Basalt pateau= Deccan trap (India).
   >Lava dome or shield Volcane = gentle slope.
   >Caldera = swimming pool of Lava with steep wall in the dome.=Kilauea Volcano(Hawai, USA)
      (Image ↓)



--Formed by Acidic Lava:
  >Less viscous or Fluid
  >Pyroclasts = explodes forming= Ash + Cinder cone= forms Crater in middle(like Caldera). (https://www.youtube.com/watch?v=Eqc2zaWS3XA) .
  >usually small volcano in groups= height <1000 feet.
 
--Composite Volcano= repetitive eruption= layers.
  >Ex- Mt. Stromboli =bcoz of frequent eruption = known as “Light hous of Mediterranean”.
         -Mt Etna in Sicily.

--Crater Vs Caldera:
   >If the top of Cone is blown off = Crater
   >If Crater enlarges in depression= Caldera.
   >Water fill = Crater/Caldera Lake = Ex- Lake Toba in Sumatra.

Some Epic Volcanic Erruption:
--Mt. Vesuvius= Bay of Naple (Itly) =24 Aug  .A.D. 79.

--Mt. Krakatau=Sunda strait (b/w Java and Sumatra), 1883 =Greatest .
        >Explosion formed Caldera(Although written in Basic Lava type ↑).
        >land was not inhabitated by any one===sound till Australia.
        >re-erupted in 1927.

--Mt. Pelee= West indies, 1902.

Facts for Valcanos:
--Mt. Cameroon = only Active volcano in West Africa.
--Atlantic coast(mostly Alpine fold mountain) has mostly= Dormant Volcano.
     >Volcano of Iceland + Azores(autonomous region of Volcano) = Active.

Geyeser Vs Hot spring:

	Geyeser	Hot Spring
Feature	Violent eruption	Just hot water
Location	3 Major areas: 1)Iceland 2)Rotorua district of North Island(New Zealand) 3)Yellowstone park(USA)	All across the globe
Famous	Wyoming, in USA (erupts in every 63 minutes avg)	Japan + Hawaii(USA)