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3.8: Key Points

  • Page ID
    35018
    • Kelly Ruppert, Tor Lacy, and Emily Haddad
    • Cerritos College, Coastline College, and East Los Angeles College

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    1. Earth’s outermost solid layer, the lithosphere, is broken into about 15 plates that move about relative to each other on the asthenosphere
    2. Oceanic lithosphere is thinner and more dense than continental lithosphere
    3. The three types of plate boundaries where the plates interact with one another are convergent (two plates collide) with compressional stress, divergent (two plates move away from one another) with tensional stress, and transform (two plates slide past one another) with shear stress
    4. Divergent boundaries start as rift valleys and ultimately result in the formation of an ocean; volcanic activity is present during all phases
    5. Convergent boundaries occur between two continental plates and result in the formation of mountains, between two oceanic plates and result in the formation of a volcanic island arc, and between one oceanic and one continental plate and result in the formation of a continental volcanic arc
    6. Passive margins are coastlines without a plate boundary and is a site with no tectonic activity
    7. Active margins are coastlines with a plate boundary where volcanism, earthquake activity, and/or mountain building occur
    8. The majority of earthquakes and volcanic activity occur on plate boundaries

    This page titled 3.8: Key Points was last modified on Wed, 24 Sep 2025 17:11:50 GMT and is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Kelly Ruppert, Tor Lacy, and Emily Haddad via source content that was edited to the style and standards of the LibreTexts platform.