Reason for volcanism in Galapagos
Three tectonic plates moving with different velocities into three different directions. Formation of Galapagos fracture zone on sea floor. Multiple hot spot. (Hot spot: local thermal convection current within earth).
NAZCA: Plate moving over hot spots. Successive formation of oceanic islands. Approximate age of island 3 - 4 Million years.
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II. Formation of aceanic island by succesive lava flows
1.- Submarine stage
2.- Subaerial Stage
First lava flows above sea level. Where hot lava hits water. Cools down quickly steep edges.
3.- Tumenescence (Swelling) Intrusion of magma into fractures swelling
radial fissures around central vent
4.- Caldera Development Magma contracts into lava reservoirs, lava pipes and dikes top weakened collapse in big blocks. Fernandina 1968, Cerro Azul, Wolf.
5.- Degradation (decline).
Declining in structures caldera filled with sediment Santa Cruz , San Cristobal
Surface currents around the Islands driven by NE and Se – Trade Winds. From June to December prevailing SE - Trade. Winds which drive the Ecuatorial Front up North. Galapagos influenced by cold water. December to June prevailing Ne- Trade winds drive Ecuatorial Front down South. Galapagos influenced by warm water out of bay of Panama .
Cromwell Current (Ecuatorial Undercurrent ):
Undercurrent bringing very cold and nutrient rich water to the Islands all year round.
Origin: 200 mt. of depth off the coast of Japan ; about 300 Km. wide reaches watersurface west of Fernandina and causes crown of upwelling; all around the Galapagos.
Responsible for main ocurrence of penguins and flightlesh cormorants in area Fernandina and Isabela.
Temperature: 15 - 18 °C, Salinity: 35.5 %.
Warm water flow out of Bay of Panama (mainly in December around Christmas - The Child!) bringing nutrient deficient water of low salinity to the Galapagos. El Niño caused by accumulation of warm water in Bay of Panama , or as Seiche or Kelvin wave within the Pacific Ocean .
Effect on the Galapagos: Hardly any. Penguins most probably don't breed in Niño Years and sharks become more aggressive due to lack of food.
Effect on Peru : El Niño reaches down as far as Callao Peruvian Guanobirds die, because fish migrates into deeper and and colder water. Peruvian fisheries suffer considerably.
Temperature: 25 - 29°C, Salinity: 35.5 - 34%.
Climate influenced by change of wind and current system. JUNE to DECEMBER (Dry or GARUA Season). Warm tropical air over cold water leads to formation of an inversion layer due to heat exchange ocean - atmosphere. The inversion layer consist of cold and moist air whose upper limit is a stratus cloud layer in aprox. 200 m. height.
(GARUA) GALAPAGOS : Where this layer hits one of the higher islands it is forced upwards. Main precipitation in highlands due to condensation of water vapor caught in clouds
Rainshadow Effect: Northern side of island in rain shadow of south. Less humidity on the northern sides of the islands. Vegetation zones reach higher in the northern side than on the south. Island of Santiago in the rainshadow of Santa Cruz .
(Wet or Rainy Season): Cumulus clouds formed by normal convection in Bay of Panama are driven to the Galapagos by the North East Trade winds. Main precipitation in the coastal areas of the northern sides of the islands. ITCZ wanders North or South according to the prevailing wind system.