The generally fully accepted theory
that the solid earth’s surface or crust
is divided into several segments
(plates) that are in relative motion.
A divergent/spreading boundary is where the
tectonic plates are separating. Some spreading
boundaries are places where the crust is sinking
downward as it is stretched thin - like in the East
Rift Valley of Africa, where the Dead Sea is
located. These are places where volcanic activity
is at a premium because the crust is being torn
open (as in splitting and cracking, like an egg
breaking open). New crust is forming when
molten lava from deep down oozes out of the
cracks where the plates are coming apart . Long
chains of undersea mounts (the world's longest is
the mid-Atlantic Ocean Ridge) and volcanic
islands typically characterize these type of plate
The transverse boundaries are places
where the two plates are just sliding past
each other, like two ships passing on the
water . In many of these boundaries there
is a lot of tension and strain where the
two plates are sliding and scraping past
each other. The resulting strain from the
sliding action of the plates causes cracks
in the crust called faults. As the larger
plates move past each other some chunks
of crust and overlying rock are broken into
fault blocks. When there is a big enough
movement along the cracks or faults in
the earth's crust we feel it in the form of
A converging boundary is the opposite of a
spreading boundary. Typically you will see
a converging boundary on a tectonic plate
that is on the opposite side of a spreading
boundary - of course! The two plates
collide upon meeting and then the heavier
one will sink or subduct into the mantle
below the lighter one. This causes
earthquakes and volcanoes to be formed.
The N. American plate is converging with
the Caribbean plate to form the L. Antilles.
The unwanted removal of soil particles
from one area to another leading to
negative environmental and socio-
ICE: Moving glaciers can scrape
valley surfaces removing top soil.
SHORELINE: Waves; tides and
sea-level changes can redistribute
ANTHROPOGENIC: Man through
his activities can remove soil
particles eg. excavating.
heavy rains on weak soil: rain drops loosen soil
particles and water transports them down hill.
vegetation depleted by drought: rain drops are free to
hit the soil, causing erosion during rainfall. Winds blow
away the fine particles during droughts.
steep slopes: gravity 'pulls harder': water flows faster;
soil creeps, slips or slumps downhill.
sudden climate change
• rainfall: erosion increases unexpectedly rapidly as rainstorms
become more severe.
• drought: water dries up and the soil becomes a playball of
winds. Soil biota die. A sudden rain causes enormous
• changing winds: areas previously sheltered, become
change of land (deforestation): the land
loses its cover, then its soil biota, porosity and
intensive farming: the plough, excessive
fertilizers and irrigation damage the land, often
housing development: soil is bared; massive
earthworks to landscape the subdivision; soil is
on the loose.
road construction: roads are cut; massive
earthworks, leaving scars behind. Not enough
attention paid to rainwater flow and
maintenance of road sides.
The process whereby measures are
adopted or implemented to prevent
soil erosion. These measures can
1. Engineering: Altering the gradient
of the land.
2. Agronomic: Incorporating good
farming practices and vegetation.
3. Policy: Laws and regulations.
Cutting the slope into steps so as to
break the flow of run-off.
Using boulder-filled wire baskets to
support unstable stream banks and
Using loose boulders to protect the
shoreline by wave/tidal impacts. The
boulder helps to dissipate energy.
Using ploughs along the contours or hill
slope rather than up-down or vertical. The
former breaks the flow of run-off whilst
the latter produces rills to increase run-
Also known as conservation tillage, is a way of
growing crops from year to year without
disturbing the soil through tillage.
In no-till farming the soil is left intact and crop
residues are left in the fields. Variations of the
conservation tillage method involve some
working of the soil with attention paid to keeping
soil compaction and carbon loss at a minimum.
These variations include reduced tillage, in
which small strips may be plowed to allow space
for planting seeds. Other terms, such as
incomplete tillage and minimal tillage may be
Strip farming is a method of farming
used when a slope is too steep or too
long, or when other types of farming
may not prevent soil erosion. Strip
farming alternates strips of closely
sown crops such as hay, wheat, or
other small grains with strips of row
crops, such as corn, soybeans,
cotton, or sugar beets. It is also
known as strip cropping.
A windbreak, or shelterbelt, is
usually made up of one or more rows
of trees planted in such a manner as
to provide shelter from the wind and
to prevent soil erosion. They are
commonly planted around the edges
of fields on farms.
A drought occurs when the average
amount of precipitation for a region
drops far below the normal amount
resulting in adverse environmental
and socio-economic effects.
CARIBBEAN 1973 and mid 80s
Bush fires eg. Approx. 50% of the Valencia/Matura forest
reserve was destroyed. Loss of biota.
Pipe-borne water supply is disrupted. WASA had to regulate
the normal supply.
Agricultural production decreased. Dairy industry affected
by heat-stress and poor quality pastures. Farmers could not
Industries suffered because of lack of water for cooling
Human resource affected leading to a loss in productivity
(discomfort; associated diseases etc.)
Soil erosion increased.
NB: 1978 Drought in Brazil caused US$ 5,700 millions in
The power of Ivan, lost homes and possessions caused
emotional trauma and shock. Counseling had to be
Looting created further disruption and prisoners escaped
causing a breakdown in law and order. A state of
emergency was declared with curfew.
80-90% of houses were damaged or destroyed and up to
8,000 had to sleep in shelters.
There was loss of electricity and limited supply of potable
water. Water was also contaminated. Most landline
telephones were put out of service and radio transmitters
were blown down.
Roads were blocked and the airport partially destroyed and
The recently built national stadium was damaged.
Estimated damage put at US$ 815 million or 200% of GDP.
Tourism sector affected. Out of 1,700 hotel rooms, only
three remained in service. Cruise ship port damaged.
Nutmegs, the main farm export had 90% of the plantations
Tax revenue was reduced .
Insurance premiums went up.
In the US offshore oil platforms were destroyed reducing
outputs in production.
This occurs when a population becomes
fragmented or separated during a natural
disaster due to evacuation and migration.
Families are broken-up.
Culture and traditions are lost.
Trauma and emotional stress occurs.
Refugees have difficulty settling in new
territory (jobs; new cultures etc)
. The 1995-2004 Soufriere volcano
disturbances in Montserrat saw the
displacement of approx. 8,000
people or 76% of the population. The
majority of them went to Britain and
PROTECT COASTLINE: A well-developed fringing reef is a self-
constructed, self-repairing breakwater, which protects the
coastline and beaches from erosion. Waves loose much of their
erosive power when they break on the reef. Also, much of the
sand like on west coast Barbados, is derived from corals which
helps to protect the coastline.
FISHING INDUSTRY: Coral reefs provide a habitat for marine life,
including fish and shellfish. Species such as conch and lobster are
important resources for the fishing and associated tourism
RECREATION & TOURISM:Photography; scuba diving; snorkeling
HERITAGE: Buccoo reef, Tobago part of the island’s pride.
SCIENCE & RESEARCH