Impact on Geographical Phenomena

• Plate Tectonics


  Theory that suggests the Earth's outer crust moves over the molten layer beneath it, and that earthquakes and volcanoes are related in their origin

  
• Earth's crust


  • Consists of large slabs of rocks (plates) whose movements are capable of folding mountains or influencing events such as earthquakes and volcanoes

  
• In the Caribbean, movement commonly occurs along divergent, convergent and transform boundaries
• Earth's crust consists of large and smaller plates, with oceans and land masses being carried on plates. The Caribbean Plate is one of the smaller plates
• Plate margins or boundaries result in various tectonic activities when one plate meets another, making the Caribbean a hotspot for volcanic and seismic activity

  
• Scientists discovered that new crust was being formed at certain places on Earth's surface, and plate margins are formed due to convection currents in the mantle

  
• Divergent plate margins


  Plates that move away from each other, resulting in a line of submarine volcanoes and fissures. Sea-floor spreading was first detected at these margins, leading to the development of plate tectonics

  
• Convergent plate margins

  Crust is being consumed or pushed back into the mantle through subduction. Plates collide and one plate rides over the other, forcing it downwards into the subduction zone. This friction generates immense heat, melting crustal rocks and molting the rock material
• Transform plate margins

  Plates slide past each other, causing pressure to build in rocks, leading to earthquake activity when rocks move suddenly to relieve stress
• The Caribbean Plate is an oceanic tectonic plate beneath Central America and the Caribbean Sea, bordered by the North American, South American, and Cocos plates

  
• The convergent margin along the Lesser Antilles is a double island arc with mountainous, volcanic islands in the inner arc and flat, low-lying limestone islands in the outer arc
• The eastern boundary of the Caribbean Plate is a subduction zone where the North and South American plates subduct beneath the Caribbean plate, forming volcanic islands like the Lesser Antilles

  
• The southern boundary of the Caribbean Plate interacts with the South American plate, forming Trinidad on the South American plate and Tobago on the Caribbean plate
• The presence of deep ocean trenches off Cayman, Puerto Rico, and Hispaniola indicates major plate boundaries with the potential for serious earthquakes of 7.5 and higher

  
• The meeting of convergent and transform margins at the southern margin of the Caribbean Plate is responsible for the extreme faulting and unstable nature of rocks in Trinidad and northern Venezuela

  
• There are about 17 active volcanoes in the Eastern Caribbean, connected at a subterranean level along the plate margin
• Positive impacts of plate tectonics in the Caribbean

  • Soils rich in nutrients useful to agriculture
  • Attractive scenery and fold mountains bring tourists
  • Access to valuable minerals, including gold, silver, nickel, bauxite, oil and gas
  • Tourists attractions: Sulphur Springs in St. Lucia, they generate income along with associated merchandise such as beauty products
  • Minerals such as oil, natural gas and asphalt can be created or brought to the surface by collision between land masses
• Negative impacts of plate tectonics in the Caribbean

  • Gigantic waves – tsunamis destroy costal areas up to 2 km inland
  • Poisonous gases around the volcanic vent prevent plant growth and cause acid rain
  • Can set back development because of the cost and time needed to rebuild
  • Explosions of hot lava, ash and gases from an erupting volcano called pyroclastic flow smother everything in their path
  • Earthquakes can shake the ground and cause buildings to collapse through landslides, liquefication or fires
• The Caribbean people are vulnerable to the impact of natural hazards because many countries are small and resources are scarce
• Affected countries needs important political decisions to be made and this puts leadership under pressure
• Tourism also takes a major blow any time there is a natural disaster in the region because tourists view the 'Caribbean' as a whole
• To help combat the negative impacts, individual countries invest in local offices and regional bodies, such as the Caribbean Disaster Emergency Management Agency (CDEMA), that coordinates emergency management systems
• Earthquakes


  Occur when rocks release energy due to pressure build-up, such as plates colliding, sliding past each other, or being pushed away by upwelling magma. This energy can cause extreme displacement of rocks, often leaving trenches along fault lines, which can have adverse consequences for populations and ocean floor
• If a major shift occurs, a tsunami can develop. Earthquakes leave fractures or faults in rocks, indicating weaknesses and potential future earthquakes. Major faults at plate margins, such as in the Caribbean, indicate weak rocks and crustal instability
• Reasons why earthquakes may be more destructive

  • Larger population living in vulnerable areas
  • The construction of more high-rise buildings
  • Unauthorized construction conducted with poor standards
  • Building with weak foundations/ built on steep land
• Richter scale


  A mathematical calculation used to measure earthquake magnitude, but most geologists and volcanologists now use the moment magnitude scale (MMS). An earthquake measuring 5.0 on the MMS is ten times stronger than one measuring 4.0
• Minor earthquakes are below 5.0, and destructive ones occur above 6.0. The largest recorded earthquake was in Chile in 1960, with a magnitude of 9.5 MMS
• Strategies to mitigate and predict earthquakes

  • Focusing on construction materials, strict building codes, and site geology
  • Encouraging building companies and citizens to adhere to strict building codes and to contrast to withstand the effects of an earthquake
  • Passing supplementary budgets to repair damage caused by earthquake
  • Imposing strict building regulations for high-rise buildings
  • Ensuring utilities can be easily turned off by installing electricity main breaker, gas valve and main water valves
  • Designing buildings to sway or bolt the structure to solid foundations
  • Developing education programs and awareness campaigns, including school evacuation drills
• Prediction efforts have made progress, for example in in China, observations such as water level in deep wells, unusual animal behavior, and radioactive gas presence have been used to predict some earthquakes. However, it is not a precise science, as it is impossible to predict the epicenter of an earthquake
• Volcanoes

  An opening in the Earth's crust allows ash, lava, steam and hot gases to escape to the surface, creating a dangerous atmosphere. Over time these eruptions build a cone shaped mountain
• Before volcanic eruptions occur, there is usually some kind of warning of increased volcanic activity, such as a tremor. In the Eastern Caribbean, along the volcanic island arc, active volcanoes have been erupting for hundreds of years
• These volcanoes produce violent eruptions and acid lava, which can be unpredictable in terms of their length of eruption and degree of severity
• Eruptions can vary from just a little steam to a few years of deadly pyroclastic flows. Sometimes major towns are destroyed (such as Plymouth, the capital of Montserrat, in 1995)
• In Montserrat, the Soufrière Hills volcano started erupting in 1995. This caused an emergency evacuation of parts of the islands, including its capital and main port, Plymouth, and then, following the permanent disruption to economic and day-to-day life on the island, led to the migration of most of the population to Great Britain
• Positive impacts of volcanoes

  • Volcanic rocks over a period of time form highly fertile soils with minerals that plants require, thus encouraging agriculture in high-risk areas and future abundant yields of crops
  • Most of the metallic mineral mined in the world – gold, silver, copper, lead, zinc are associated with magmas found deep within the roots of extinct volcanoes
• Negative impacts of volcanoes

  • Poisonous gases around the volcanic vent and aid rain prevent plant growth. This leads to the destruction of the agricultural sector and export sectors
  • Ash fallout damages plants and crops by blocking out sunlight and causes a high incidence of sickness and respiratory ailments
  • Damage to beaches or vegetation resulting from lava flows and possible damage to coral and marine ecology affects tourism and the fishing industry
  • Migration of people from the country at risk to other regional countries or to the metropole
• Volcanic rocks over a period of time form highly fertile soils with minerals that plants require, thus encouraging agriculture in high-risk areas and future abundant yields of crops. It contributes to the production of abundant food and civilization.
• Damage to beaches or vegetation resulting from lava flows

  Affects tourism and the fishing industry
• Most of the metallic mineral mined in the world – gold, silver, copper, lead, zinc are associated with magmas found deep within the roots of extinct volcanoes.
• Migration of people from the country at risk to other regional countries or to the metropole

  For example, the Montserrat disaster of 1995 caused forced migration, both internal (to other areas of the country) and external (such as to the UK). The former led to competition for or insufficient infrastructure and social services.