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1ST-Q-Science-10-LAS

Distribution of Active Volcanoes, Earthquakes, Epicenters, and Major Mountain Belts

  1. Volcanoes: Distribution is not random; they are concentrated in specific zones.

    • Ring of Fire: A major area in the basin of the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur. It is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and plate movements.

    • Mid-Ocean Ridges: Underwater mountain systems formed by plate tectonics. They are associated with seafloor spreading and are the sites of frequent earthquakes.

    • Hot Spots: Volcanic regions thought to be fed by underlying mantle plumes. These can occur far from plate boundaries (e.g., Hawaii).

  2. Earthquakes: Associated with plate tectonics and fault lines.

    • Plate Boundaries: Most earthquakes occur along the edges of tectonic plates. The type of boundary (convergent, divergent, transform) influences the nature and frequency of earthquakes.

    • Fault Zones: Areas where the Earth’s crust is broken by faults. Earthquakes often occur along these faults when the rocks suddenly slip.

  3. Epicenters: Points on the Earth’s surface directly above the focus (hypocenter) of an earthquake.

    • Mapping Epicenters: Helps to define active seismic zones and plate boundaries. High concentrations of epicenters indicate areas of significant tectonic activity.

  4. Major Mountain Belts: Formed by tectonic activity, particularly at convergent plate boundaries.

    • Formation: Orogenesis (mountain building) occurs through the collision of tectonic plates, causing folding, faulting, and uplift of the Earth’s crust.

    • Examples: The Himalayas (formed by the collision of the Indian and Eurasian plates), the Andes (formed by the subduction of the Nazca plate under the South American plate), and the Alps (formed by the collision of the African and Eurasian plates).

  5. Relationship between Volcanoes, Earthquakes, and Mountain Belts

    • Tectonic Plates: All three phenomena are related. Plate movements cause earthquakes, create volcanic activity, and result in the formation of mountain belts.

TYPE OF PLATE BOUNDARIES

  1. Convergent Boundaries: Regions where tectonic plates collide.

    • Oceanic-Oceanic: One plate subducts under another, forming deep ocean trenches and volcanic island arcs.

    • Oceanic-Continental: The denser oceanic plate subducts under the continental plate, leading to the formation of volcanic mountain ranges and trenches.

    • Continental-Continental: Plates collide and compress, resulting in the formation of large mountain ranges.

  2. Divergent Boundaries: Areas where tectonic plates move apart.

    • Seafloor Spreading: Magma rises from the mantle to create new crust, forming mid-ocean ridges.

    • Continental Rifting: A continent begins to split apart, forming rift valleys that can eventually become new ocean basins.

  3. Transform Boundaries: Locations where plates slide past each other horizontally.

    • Fault Zones: Characterized by frequent earthquakes as the plates grind against each other.

Convection currents

  • These are the primary forces driving the movement of tectonic plates.

    • Within the Earth's mantle, heat from the core causes rock material to become less dense and slowly rise. As it approaches the crust, it cools, becomes denser, and sinks back down. This continuous cycle of rising and sinking hot material creates slow-moving circulatory currents, similar to boiling water.