Plate Tectonics, Volcanoes, Earthquakes, and Disaster Management

Vocabulary practice flashcards covering internal structure of the Earth, plate tectonics, convergent, divergent, and transform boundaries, volcano types, earthquake properties, and disaster management strategies based on Ms Nurul's lecture notes.

Plate Tectonic Theory

A geological theory explaining how internal forces within the Earth cause tectonic plates to move around the world.

Earth Core

The innermost layer of the Earth, which has the highest temperature ($4400 - 6000^\circ\text{C}$) and is the thickest layer at $3300\,\text{km}$.

Earth Mantle

The middle layer of the Earth located between the core and crust, featuring temperatures ranging from $1000 - 3700^\circ\text{C}$ and a thickness of $2900\,\text{km}$.

Earth Crust

The outermost layer of the Earth, which is the thinnest ($6 - 70\,\text{km}$) and has the lowest temperature of all layers.

Oceanic Crust

Denser crust located beneath deep oceans, measuring $5 - 8\,\text{km}$ thick and composed of basalt formed from rapidly cooled magma, with rocks less than $200\,\text{million}$ years old.

Continental Crust

Less dense crust located beneath landmasses and shallow seas, measuring $30 - 60\,\text{km}$ thick and composed of granite, with rock ages ranging up to nearly $4\,\text{billion}$ years old.

Convectional Currents

Movements of heat within the mantle where material heated by the core expands, rises, and spreads beneath plates, dragging them apart before cooling and sinking to repeat the process.

Slab-Pull Force

The force occurring at convergent boundaries where denser oceanic crust is pulled down by gravity into the mantle, sinking under its own weight and dragging the trailing plate along.

Seafloor Spreading

Process occurring when two oceanic plates diverge, allowing magma to rise through mid-oceanic ridges to cool and create new oceanic crust, pushing older crust outward on both sides.

Magnetic Striping

The pattern of alternating normal and reversed magnetic bands in ocean crust formed as iron minerals in cooling lava align with Earth's magnetic field during seafloor spreading.

Seafloor Spreading and Magnetic Striping Diagram

Diagram illustrating magma intruding at an oceanic ridge spreading center, showing symmetrical age distribution and alternating positive and negative magnetic polarity bands in new oceanic lithosphere.

Convergent Plate Boundary

A plate boundary where tectonic plates move towards each other, becoming faulted, folded, or subducted.

Oceanic-Oceanic Convergent Boundary

Boundary where two oceanic plates collide and the denser plate subducts, forming a deep oceanic trench, subduction-zone melting, volcanic island arcs, and earthquakes (e.g., Mariana Trench).

Continental-Continental Convergent Boundary

Boundary where two thick, buoyant continental plates collide with immense compressional force, resisting subduction and buckling or folding upward to form fold mountains (e.g., Himalayas).

Fold Mountain Structure Diagram

Diagram showing compressional forces buckling continental crust to form fold mountains, detailing an upfold known as an anticline and a downfold known as a syncline.

Oceanic-Continental Convergent Boundary

Boundary where denser oceanic crust subducts beneath lighter continental crust, forming an oceanic trench, volcanoes on the continental crust, and fold mountains (e.g., Sunda Trench and Barisan Mountains).

Divergent Plate Boundary

A plate boundary where tectonic plates move away from each other.

Oceanic-Oceanic Divergent Boundary

Boundary where oceanic plates pull apart, decreasing overlying pressure to melt mantle material into magma that forms mid-oceanic ridges and new ocean floor (e.g., Mid-Atlantic Ridge).

Rift Valley

A linear depression with steep sides formed along continental-continental divergent boundaries when stretched crust fractures into faults and the central block sinks (e.g., East African Rift Valley).

Transform Plate Boundary

A plate boundary where tectonic plates slide past each other along transform faults, accumulating tremendous stress that is released as earthquakes (e.g., San Andreas Fault).

Shield Volcano

A broad and wide volcano with gentle slopes made mostly of lava layers, formed at divergent boundaries from low-silica, runny magma that releases gas easily during effusive eruptions.

Shield Volcano Structure Diagram

Structural diagram of a shield volcano, featuring gently sloping sides, a central vent leading to a crater, and accumulated layers of ash and lava from successive quiet eruptions.

Stratovolcano

A tall, steep-sided volcano made of alternating layers of lava and ash, formed at convergent boundaries where viscous, high-silica magma traps gas to cause explosive eruptions.

Stratovolcano Structure Diagram

Structural diagram of a stratovolcano showing steep sides, alternating layers of lava, ash, and fragmented material, a main crater, a secondary cone, and a magma conduit.

Volcanic Explosivity Index (VEI)

A logarithmic scale from $0$ to $8$ measuring volcanic eruption strength based on ejected material volume, cloud height, and eruption duration, where an increase of $1$ indicates a $10\text{-fold}$ energy increase.

Pacific Ring of Fire

A major belt along convergent plate boundaries around the Pacific Ocean containing the world's highest concentration of active volcanoes and earthquakes.

Hotspot Volcanoes

Volcanoes formed away from plate boundaries where unusually hot magma rises directly from deep mantle plumes through the overlying crust (e.g., Hawaii).

Tephra

Volcanic materials including ash, rock fragments, and volcanic bombs ejected into the atmosphere during an eruption.

Lahars

Fast-moving mudflows created when loose volcanic ash and debris mix with water from heavy rain or melting snow.

Pyroclastic Flows

High-speed, extremely hot clouds of gas, ash, and rock fragments moving rapidly down volcanic slopes during explosive eruptions.

Geothermal Energy

Energy derived from heat within the Earth's crust, where groundwater heated by hot rocks turns into steam or hot water to drive turbines for electricity.

Earthquake Focus

The exact underground location within the Earth's crust where an earthquake originates and seismic energy is first released.

Earthquake Epicenter

The point on the ground surface directly above the focus of an earthquake.

Fault

A fracture or weak point within a tectonic plate along which rock masses slip when built-up pressure is released.

Earthquake Anatomy Diagram

Diagram illustrating the structural elements of an earthquake, showing the focus underground, fault line, epicenter at the ground surface, and radiating seismic waves.

Richter Scale

A logarithmic scale measuring the maximum ground shaking intensity recorded during an earthquake, primarily suited for small, local events.

Moment Magnitude Scale ($M_w$)

A logarithmic scale measuring the total energy released by an earthquake, offering higher accuracy than the Richter scale for large earthquakes.

Soil Liquefaction

A hazard where violent ground shaking causes water-saturated loose soil to lose strength and behave like a liquid, causing structures to sink or tilt.

Tsunami

A series of ocean waves triggered by seabed earthquakes that move at high speeds (up to $800\,\text{km/h}$) in deep water and grow dramatically in height (up to $15\,\text{m}$) in shallow coastal zones.

Land Use Planning

A pre-disaster strategy using hazard maps to restrict or control development in vulnerable areas or relocate existing structures to safer locations.

Hazard-Resistant Building Designs

Engineering measures—such as shock absorbers, weighted dampers, reinforced steel diagonal cross-braces, and deep foundations—designed to prevent building collapse during seismic activity.

Monitoring & Warning Systems

Technologies using sensors, scientific instruments, and satellites to detect early seismic or volcanic activity and broadcast alerts through sirens or mobile broadcasts.

Search and Rescue

An immediate post-disaster response utilizing specialized tools such as heat sensors, listening devices, and sniffer dogs to locate and save trapped victims.

Provision of Social and Psychosocial Services

Post-disaster response providing essential physical supplies (clean water, food, medical care) and mental health services (counseling, therapy) to help survivors recover.

Restoring and Improving Facilities

A long-term disaster recovery strategy focusing on rebuilding infrastructure and housing with enhanced hazard-resistant specifications to minimize future risk.