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9th grade · Science · Unit 17 of 28

Plate Tectonics

Earth's layers, moving plates and the age of rocks.

What your child practices

Practices modeling Earth's interior from seismic evidence, how convection in the mantle moves plates, what happens at each kind of plate boundary, and why ocean crust is young while some continental rock, like the Adirondacks', is over a billion years old.

New York State Learning Standards learning standard: HS-ESS2-1; HS-ESS2-3; HS-ESS1-5 · Earth's layers and the movement of plates, how plate motion builds and wears down landforms, and the ages of crustal rocks

How we explain it

Children can open this short lesson before they practice.

  1. Earth’s layers from the outside in: crust, mantle, outer core (liquid), inner core. Seismic waves reveal them.
  2. Convection in the mantle moves the plates.
  3. New ocean crust forms at ridges, so ocean crust is young. The Atlantic is slowly getting wider.

Example: Which layer of Earth is liquid? Some seismic waves can’t pass through it. It is the layer around the inner core. Answer: the outer core

Plate Tectonics in New York

In the New York State Learning Standards, this is unit 17 of 28 in 9th grade Science, after Populations & Evolution and before Earth's Early History.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: New York State Education Department (NYSED)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    The rigid outer shell of Earth that is broken into plates is the…

    • outer core
    • hydrosphere
    • lithosphere
    • atmosphere

  2. Question 2

    At a transform boundary, plates…

    • collide head-on
    • pull apart
    • stop moving
    • slide past each other

  3. Question 3

    Most earthquakes and volcanoes happen…

    • along plate boundaries
    • evenly everywhere
    • only at the poles
    • in the middle of plates

  4. Question 4

    Heat and pressure deep underground change rock into…

    • soil
    • sedimentary rock
    • metamorphic rock
    • igneous rock

  5. Question 5

    At a mid-ocean ridge, plates…

    • collide and build mountains
    • stop moving
    • move apart and new crust forms
    • sink into the core

  6. Question 6

    Ocean crust is rarely older than about 200 million years because…

    • it never forms
    • it floats higher than continents
    • it is made of ice
    • it forms at ridges and is destroyed at subduction zones

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