ECOSYSTEMS > COASTAL WATERS > CONTINENTAL SHELF
The hard outer crust of the Earth (known as the lithosphere) is covered with a series of plates which float on the soft layers of the Earth’s mantle. These plates may move away from each other, creating deep trenches between them. Other times they may crash together, although at a rate too slow to see with the naked eye — about 4 inches or 100 mm per year on average.
Despite the relatively slow movement, the tremendous weight and mass of the plates means impact areas are often characterized by wide-scale geological events such as seaquakes (underwater earthquakes), volcanic activity and the formation of mountains.
Types of Plate Boundaries
Divergent Boundaries: When plates move away from each other, they form a Divergent Boundary. These areas widen with time and are often characterized by the formation of rifts and ridges as a new boundary is created between them. The Mid-Atlantic Ridge is an example of a divergent boundary between the North and South American continental plates on the west side of the Atlantic Ocean and the Eurasian and African plates on the east side.
Convergent Boundaries: These boundaries occur when plates grind toward each other. As their leading edges impact, violent geological activity occurs, including earthquakes and volcanic activity. Often one plate will slide on top of the other, creating a subduction zone characterized by deep marine trenches. Oregon has been repeatedly affected by the subduction of the Juan de Fuca plate by the larger and heavier North American continental plate. This deep sea activity has produced devastating earthquakes and tsunami in the past.
Transform Boundaries: These boundaries occur when plates slide passed each other. Because the impact is more of a grinding action, the boundary may not have the dramatic geological features of a Divergent or Convergent Boundary. Instead, a transform fault may occur between the two plates, often looking like a deep zig-zag break in the Earth’s crust. The majority of these faults are hidden beneath the sea, but the famous San Andreas fault in California is an example you can see with your own eyes. These boundaries often cause strong and frequent earthquakes.
Plate Boundary Zones: This mixed type boundary occurs when the effects of plate movements are not clear or may show different types of effects at different times.
The hard outer crust of the Earth (known as the lithosphere) is covered with a series of plates which float on the soft layers of the Earth’s mantle. These plates may move away from each other, creating deep trenches between them. Other times they may crash together, although at a rate too slow to see with the naked eye — about 4 inches or 100 mm per year on average.
Despite the relatively slow movement, the tremendous weight and mass of the plates means impact areas are often characterized by wide-scale geological events such as seaquakes (underwater earthquakes), volcanic activity and the formation of mountains.
Types of Plate Boundaries
Divergent Boundaries: When plates move away from each other, they form a Divergent Boundary. These areas widen with time and are often characterized by the formation of rifts and ridges as a new boundary is created between them. The Mid-Atlantic Ridge is an example of a divergent boundary between the North and South American continental plates on the west side of the Atlantic Ocean and the Eurasian and African plates on the east side.
Convergent Boundaries: These boundaries occur when plates grind toward each other. As their leading edges impact, violent geological activity occurs, including earthquakes and volcanic activity. Often one plate will slide on top of the other, creating a subduction zone characterized by deep marine trenches. Oregon has been repeatedly affected by the subduction of the Juan de Fuca plate by the larger and heavier North American continental plate. This deep sea activity has produced devastating earthquakes and tsunami in the past.
Transform Boundaries: These boundaries occur when plates slide passed each other. Because the impact is more of a grinding action, the boundary may not have the dramatic geological features of a Divergent or Convergent Boundary. Instead, a transform fault may occur between the two plates, often looking like a deep zig-zag break in the Earth’s crust. The majority of these faults are hidden beneath the sea, but the famous San Andreas fault in California is an example you can see with your own eyes. These boundaries often cause strong and frequent earthquakes.
Plate Boundary Zones: This mixed type boundary occurs when the effects of plate movements are not clear or may show different types of effects at different times.