Plate Tectonics: mapping the cause of natural disasters

Section role: Supports Section 3 ('Mapping the Cause') while the teacher formalizes the concepts students observed during the sand-tray exploration in Section 2. The presentation overlays the locations of the disasters shown in the Section 1 video onto a global tectonic plate map, revealing the correlation that disasters are not random but cluster at plate boundaries. The teacher uses these slides to introduce formal vocabulary (lithosphere, convection currents, convergent/divergent/transform) and to answer the central Section 3 question: 'Why did the buildings on loose sand fail faster?' Slide outline: 1. **Title: 'Plate Tectonics—Why Earth Shakes'** — Opens with a visual of a cracked building and poses: 'What is underneath the soil that causes all that motion?' Sets the frame that the slides will explain the mechanism hidden inside Earth. 2. **Earth's Structure** — Cross-section diagram labeling the crust (thin, solid), mantle (hot, slowly flowing rock), and core (the heat engine). Bullets: 'The core is extremely hot.' 'Heat flows upward through the mantle.' 'All Earth's surface motion is powered by this internal heat.' 3. **Convection Currents: The Engine** — Animated-style diagram of the mantle showing warm rock rising and cool rock sinking in circular patterns. Bullet: 'Like boiling water in a pot, the mantle's hot material moves upward and pushes the plates floating on top; cool material sinks back down.' Relates to 7th-grader experience with thermal motion. 4. **The Lithosphere and Plate Boundaries** — Global map highlighting the major tectonic plates (Pacific, North American, Eurasian, African, Antarctic, Indo-Australian, South American) and their boundaries drawn as bold lines. Bullets: 'The lithosphere is Earth's brittle outer shell—crust plus the top of the mantle.' 'It is broken into large plates that fit together like a jigsaw puzzle.' 'These boundaries are where we find most earthquakes and volcanoes.' 5. **Convergent Boundaries: Plates Collide** — Diagram showing two plates moving toward each other, with one sliding beneath the other (subduction). Bullets: 'At convergent boundaries, plates crash together.' 'One plate is forced under the other in a process called subduction.' 'This creates the deepest ocean trenches and the largest earthquakes.' Visual should include a label for 'subduction zone' and show the descending plate creating heat and magma. 6. **Divergent Boundaries: Plates Pull Apart** — Diagram showing two plates moving away from each other, with new crust forming in the gap (mid-ocean ridge). Bullets: 'At divergent boundaries, plates move apart.' 'New crust erupts and cools, pushing the plates further apart.' 'This is where volcanic activity occurs along ocean ridges.' 7. **Transform Boundaries: Plates Slide Past Each Other** — Diagram of two plates moving horizontally in opposite directions (e.g., San Andreas Fault). Bullets: 'At transform boundaries, plates scrape alongside each other.' 'The rock builds up stress as it resists sliding, then suddenly ruptures—causing intense, frequent earthquakes.' 'The shaking is violent and can be felt far from the boundary.' Link visually to Section 2: this is the sideways shaking students felt in the tray. 8. **How Energy is Released: Seismic Waves** — Diagram of an earthquake focus (hypocenter) with concentric circles representing radiating seismic waves (label P-waves and S-waves). Bullets: 'As plates push and stress builds, energy accumulates in the rock.' 'When stress exceeds the rock's strength, it suddenly ruptures.' 'The rupture releases energy in the form of seismic waves that travel through the crust.' 'These waves cause the ground to shake—sometimes for 10 to 30 seconds.' Connect to Section 2's 10-second shake test. 9. **Disaster Hotspots: Overlay Evidence from Section 1** — A world map showing the locations of the disasters visible in the Section 1 video (e.g., a major earthquake near Japan, a volcanic eruption in Indonesia, a California earthquake) with plate boundary lines overlaid and color-coded by type (red for convergent, blue for divergent, yellow/orange for transform). Bullets: 'Notice the pattern: disasters cluster exactly at plate boundaries.' 'Earthquakes are most common near convergent and transform boundaries.' 'Volcanoes are common near convergent and divergent boundaries.' This directly validates the Section 1 observations. 10. **Why Loose Sand Fails: Linking Section 2 to Plate Tectonics** — Side-by-side cross-section diagrams: one showing a building on firm bedrock with seismic waves passing through, one showing a building on loose, water-saturated soil. Bullets: 'Seismic waves travel at different speeds through different materials.' 'When waves reach loose, wet soil, the soil grains lose contact—it behaves like a liquid (liquefaction).' 'Buildings sink and fail because the ground beneath them is no longer solid.' 'This is why your building in Section 2 failed faster on loose sand.' Directly answers the opening prompt. 11. **Misconception Check: Are Disasters Random?** — Bold text on slide: 'NO. Disasters happen where energy builds up at plate boundaries. We can predict high-risk zones.' Bullets: 'Plate boundaries are the earthquake and volcano zones on Earth.' 'Millions of people live near these zones—engineers use this knowledge to build safer structures.' 'Understanding plate tectonics helps us prepare and protect lives.' 12. **Closing Slide: Question for Discussion** — 'If you know where plate boundaries are, where on Earth would you predict the next major earthquake or volcanic eruption will happen? Use what you now know about convergent, divergent, and transform boundaries.' This hands control back to the teacher and foreshadows Section 4's focus on the Cascadia Subduction Zone and the Canadian West Coast. Concrete examples and vocabulary to surface: lithosphere, convection currents, convergent/divergent/transform boundaries, subduction, subduction zone, seismic waves, P-waves, S-waves, liquefaction, hypocenter, the disasters from the Section 1 video, the San Andreas Fault, and the Cascadia Subduction Zone (mentioned in preview). Hooks: Builds directly on Section 1's video footage (provides the 'why' for the observed disasters), explains Section 2's exploration findings (sand liquefaction and building failure on loose soil), and sets up Section 4's application task (Cascadia Subduction Zone risk assessment on the Canadian West Coast).

Lara from Teachy