Diagnostic Test: Tectonics

Plate tectonics is like a giant jigsaw puzzle — Earth’s crust is broken into pieces that move, collide, and reshape the planet.

Instructions: Attempt each question without referring to notes. Select the best answer from the four options provided. After completing all questions, check your answers against the key below.

1. The theory of plate tectonics states that the Earth’s lithosphere is divided into:

(A) Five major layers of the atmosphere (B) Several rigid plates that move over the asthenosphere (C) Three distinct layers of the Earth’s interior (D) Two hemispheres separated by the equator

2. A destructive (convergent) plate boundary occurs when:

(A) Two oceanic plates move apart (B) An oceanic plate slides beneath a continental plate (C) Two continental plates move past each other (D) Magma rises to create new crust

3. The Ring of Fire is associated with:

(A) A zone of high pressure and low temperature (B) A horseshoe-shaped zone of intense volcanic and seismic activity around the Pacific Ocean (C) The formation of new oceanic crust at mid-ocean ridges (D) Areas of significant desertification

4. A primary seismic wave (P-wave) differs from a secondary wave (S-wave) because:

(A) P-waves can travel through liquids; S-waves cannot (B) S-waves travel faster than P-waves (C) P-waves cause horizontal ground movement; S-waves cause vertical movement (D) S-waves can travel through the outer core; P-waves cannot

5. The Richter scale measures:

(A) The number of casualties from an earthquake (B) The magnitude (energy released) of an earthquake (C) The depth at which an earthquake occurs (D) The duration of an earthquake

6. A hotspot volcano forms when:

(A) Two continental plates collide (B) A mantle plume creates volcanic activity far from a plate boundary (C) An oceanic plate subducts beneath another plate (D) Magma erupts at a divergent boundary

7. Which of the following is a tectonic hazard mitigation strategy?

(A) Constructing buildings with flexible steel frames that absorb seismic energy (B) Planting trees to reduce soil erosion (C) Building sea walls to prevent coastal flooding (D) Installing early warning systems for tropical cyclones

8. The Elastic Rebound Theory explains:

(A) How volcanoes form at subduction zones (B) How stress builds up along a fault and is suddenly released as an earthquake (C) How tsunamis are generated by underwater earthquakes (D) How plate boundaries are created at mid-ocean ridges

9. A shield volcano is characterised by:

(A) Steep sides and explosive eruptions (B) Broad, gently sloping sides and effusive (non-explosive) eruptions (C) A narrow cone shape with pyroclastic flows (D) Eruption of extremely viscous, silica-rich lava

10. The Human Development Index (HDI) is most relevant to tectonic hazards because:

(A) It predicts when earthquakes will occur (B) Countries with lower HDI tend to have higher death tolls from natural hazards due to weaker infrastructure and fewer resources (C) It measures the geological risk of volcanic eruptions (D) It determines the magnitude of earthquakes

1. (B) The theory of plate tectonics proposes that the Earth’s lithosphere (crust and upper mantle) is broken into several rigid tectonic plates that float on and move over the semi-molten asthenosphere. There are seven major plates and several minor plates, moving at rates of 1-15 cm per year.

2. (B) At a destructive (convergent) boundary, two plates move towards each other. When an oceanic plate meets a continental plate, the denser oceanic plate subducts beneath the continental plate, forming a deep ocean trench and volcanic mountain ranges (e.g. the Andes). Earthquakes and volcanism are common.

3. (B) The Ring of Fire is a horseshoe-shaped zone around the Pacific Ocean where approximately 75% of the world’s active volcanoes are located and where approximately 90% of earthquakes occur. It marks the boundaries of several tectonic plates, including the Pacific, Nazca, and Philippine plates.

4. (A) P-waves (primary/compressional waves) are the fastest seismic waves and can travel through solids, liquids, and gases. S-waves (secondary/shear waves) are slower and can only travel through solids. This difference is used to determine the composition of the Earth’s interior; S-waves cannot pass through the liquid outer core.

5. (B) The Richter scale (now largely replaced by the moment magnitude scale) measures the magnitude of an earthquake, which is proportional to the logarithm of the energy released. Each whole number increase represents approximately 32 times more energy. It does not measure damage, casualties, or duration directly.

6. (B) Hotspot volcanoes form when a mantle plume (a column of abnormally hot rock) rises from deep within the mantle and creates volcanic activity in the middle of a tectonic plate, far from any plate boundary. As the plate moves over the stationary hotspot, a chain of volcanoes is formed (e.g. the Hawaiian Islands).

7. (A) Constructing buildings with flexible steel frames (base isolation, seismic dampers) is a structural mitigation strategy that absorbs seismic energy and reduces damage during earthquakes. Planting trees is a flood mitigation strategy; sea walls protect against coastal erosion and flooding; cyclone early warning systems are for weather hazards.

8. (B) The Elastic Rebound Theory (Reid, 1910) explains that as tectonic plates move, friction along fault lines prevents them from sliding past each other. Stress builds up in the rocks until it exceeds the frictional resistance, causing the rocks to snap back (rebound) to their original shape, releasing energy as seismic waves (an earthquake).

9. (B) Shield volcanoes (e.g. Mauna Loa, Hawaii) are characterised by broad, gently sloping sides formed by successive flows of low-viscosity basaltic lava that travels long distances before solidifying. Eruptions are effusive (non-explosive) with lava flows rather than pyroclastic material, due to the low viscosity of basaltic lava.

10. (B) The HDI (combining life expectancy, education, and GDP per capita) is relevant to tectonic hazard impact because vulnerability is closely linked to development. Countries with lower HDI have weaker building infrastructure, fewer emergency services, less effective early warning systems, and fewer resources for recovery, resulting in higher death tolls from the same magnitude event compared to wealthier nations.

Confusing the Richter scale with a linear scale: The Richter scale is logarithmic — each whole number increase represents approximately 10 times the amplitude and 32 times the energy released. A magnitude 7 earthquake is not “slightly worse” than a magnitude 6; it releases about 32 times more energy. Students often treat the scale as linear.

Confusing destructive and constructive plate boundaries: Constructive (divergent) boundaries create new crust as plates move apart (e.g., Mid-Atlantic Ridge). Destructive (convergent) boundaries destroy crust as one plate subducts beneath another (e.g., Pacific Plate under the Philippine Plate). The terminology refers to what happens to the crust, not whether the boundary is “good” or “bad.”

Assuming all volcanoes at plate boundaries are the same type: Volcanic type depends on the plate boundary and magma composition. Subduction zones produce explosive stratovolcanoes (viscous silica-rich magma). Divergent boundaries produce effusive shield basalt flows (low-viscosity magma). Hotspots in ocean basins also produce shield volcanoes. Match the volcano type to the tectonic setting.

• Hazards: Tectonic activity causes natural hazards
• Coastal Systems: Tectonics affect coastal landforms
• Physical Geography: Tectonics is a physical geography topic