Tectonic Plates MS-ESS2-3

Asthenosphere

The soft upper mantle layer under lithospheric plates. Asthenosphere. The asthenosphere is a hot, flowing layer of rock beneath the Earth's crust that allows tectonic plates to move.

Continental drift

The hypothesis that all the continents are moving very slowly across Earths surface. Continental drift. Continental drift is the idea that Earth's continents are slowly shifting positions over millions of years.

Geologic time scale

A timeline of Earth's history based on major changes. Geologic time scale. The geologic time scale is a system used by scientists to organize Earth's history into different periods based on significant events and changes like the appearance of new life forms or major extinctions.

Hot spot

An area where magma melts through the crust above it. Hot spot. A hot spot is a place in the Earth's crust where magma rises and creates volcanoes.

Index fossil

A fossil from an organism that existed for a short time, it is used to determine the age of other fossils. Index fossil. An index fossil helps scientists figure out how old other rocks and fossils are because it comes from a species that lived for only a short time and is found in many places.

Lithosphere

The rigid outer layer of Earth made up of the crust and upper mantle. Lithosphere. In simple terms, the lithosphere is the solid shell of Earth where we live, including the ground and the layer just beneath it.

Mid ocean ridge

A long mountain range on the seafloor formed by lava eruptions through Earths crust. Mid ocean ridge. A mid ocean ridge is an underwater mountain range formed where tectonic plates spread apart and magma rises to create new ocean floor.

Ocean trench

A deep part of the seafloor where a subducting slab bends down. Ocean trench. An ocean trench is a deep, narrow valley in the ocean floor caused by one tectonic plate sliding beneath another.

Seafloor spreading

The formation of new seafloor by magma at a mid-ocean ridge seafloor spreading. Seafloor spreading is when molten rock rises from the Earth's mantle at ocean ridges, creating new ocean floor as it spreads outwards.