What forms at each kind of plate boundary
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
India and Asia are continental plates. When two continents meet, neither subducts, and the light crust buckles upward. A student tells Jun that the Himalayas formed when India's oceanic plate sank beneath Asia. Which reply fits the card?
- Supported; the oceanic plate sinks and builds the range with volcanoes above it, as at a trench arc
- Not supported; the plates part, and the range is a rift valley formed between two continents
- Not supported; both plates are continental, so neither sinks and the crust buckles upward
- Supported; India is an oceanic plate, so it sinks and the Himalayas are a chain of volcanoes
Read this first
Card (USGS)
At a transform boundary such as the San Andreas, plates slide past each other. Crust is neither produced nor recycled there.
A student tells Kira that the San Andreas fault makes new crust as plates slide. Which reply fits the card?
- Not supported; the fault is a trench, where crust sinks
- Supported; sliding plates pull apart and new crust forms along the fault
- Not supported; plates slide past, and no crust is made or recycled
- Supported; sliding plates press together and crust is recycled along the fault
Card (example data)
Plate N lies north of the boundary and moves 3 cm a year east and 2 cm a year north. Plate S lies south of it and moves 3 cm a year west and does not move north or south.
A boundary runs east to west. Which description fits the motion, by Luz's reading?
- Mostly closing at 2 cm a year, with some sliding at 6 cm a year
- Mostly sliding past at 6 cm a year, with some opening at 2 cm a year
- Opening at 6 cm a year, with some sliding at 2 cm a year
- Sliding past at 3 cm a year, with some opening at 2 cm a year
Card (example data)
The slab moves 7 cm a year along its dip. Depth rate = speed × sin(dip). sin 60° is about 0.87.
A slab dips 60° and sinks along its dip at 7 cm a year. About how long to reach 600 km depth, by Milo's math? (1 km = 100,000 cm.)
- About 100 million years
- About 1 million years
- About 8.6 million years
- About 10 million years
Four boundary sites (example data)
Site Quake depths Volcanoes Crust ages Site W to 20 km none youngest at the center Site X to 600 km a curved chain oldest next to a deep trench Site Y to 20 km none ridge offset sideways Site Z to 100 km none continental crust on both sides Which site is a continent–continent collision, and what separates it from Site X, by Noah's reading?
- Site Z: quakes stop near 100 km and there is no volcanic chain, unlike Site X
- Site X: quakes reach 600 km and it has a curved chain of volcanoes
- Site W: quakes stop near 20 km and its crust is youngest at the center, unlike Site X
- Site Y: quakes stop near 20 km and its ridge is offset sideways, unlike Site X
Quakes 200 km inland of four trenches (example data)
Zone Depth of quakes Zone 1 168 km Zone 2 200 km Zone 3 280 km Zone 4 346 km Which conclusion does the table support, by Ren's reading? (Dip = angle whose tangent is depth ÷ 200 km.)
- The four zones share one dip of 45°, since depth rises with distance in each
- Zone 4 has the shallowest dip, since its quakes are the deepest
- Dip falls from 60° to 40° from Zone 1 to Zone 4, as depth rises
- Slab dip varies from about 40° to 60°, so no single dip fits every zone
The East African Rift is a divergent boundary, where a continent is pulled apart and a valley forms. A student says quakes along a line across a continent show a new divergent boundary. What added evidence would strengthen that, by Tala's reading?
- Deep quakes along the line, as at a trench
- A chain of volcanoes far from the line, with no sign of motion
- More quakes on one date, with no change in station positions
- GPS stations on both sides moving apart, with a lengthening valley
Card (USGS)
Divergent boundaries make ridges and rifts. Convergent boundaries make trenches, volcanic arcs and mountains. Transform boundaries slide plates past. Hotspots lie inside plates.
Which summary links boundaries to features, by Zee's reading?
- Divergent: trenches and arcs. Convergent: ridges and rifts. Transform: sliding. Hotspots: volcanoes inside plates
- Divergent: ridges and rifts. Convergent: trenches, arcs, mountains. Transform: new crust. Hotspots: volcanoes on boundaries
- Divergent: ridges and rifts. Convergent: sliding. Transform: trenches and arcs. Hotspots: volcanoes on boundaries
- Divergent: ridges and rifts. Convergent: trenches, arcs, mountains. Transform: sliding. Hotspots: volcanoes inside plates
The Marianas are ocean–ocean convergence. The Andes are ocean–continent convergence. The Himalayas are continent–continent convergence. Which summary pairs each place with its plates and features, by Ari's reading?
- Marianas: trench and island arc. Andes: trench and volcanic range. Himalayas: mountains with no trench
- Marianas: trench and island arc. Andes: mountains with no trench. Himalayas: trench and volcanic range
- Marianas: mountains with no trench. Andes: trench and island arc. Himalayas: trench and volcanic range
- Marianas: trench and island arc. Andes: trench and volcanic range. Himalayas: a rift valley
Card (USGS)
At subduction zones, earthquakes lie in a zone sloping 40 to 60° down under the overriding plate and reaching several hundred km.
Which summary of earthquakes at subduction zones fits the cards, by Bo's reading?
- Quakes deepen inland along a slab dipping 4 to 6°, reaching several hundred km
- Quakes deepen inland along a slab dipping 40 to 60°, reaching several hundred km
- Quakes stay shallow along a slab dipping 40 to 60°, reaching just a few km
- Quakes deepen toward the sea along a slab dipping 40 to 60°, reaching several hundred km