Plate Tectonics and Earth

The Dynamic Crust, Earthquakes and the Earth’s Interior
Why is the Earth’s crust described as being dynamic?
Crust- solid rock outer zone of Earth
The crust is part of the lithosphere.
The Earth’s crust is dynamic which means constantly changing.
Earthquakes
Volcanoes
Crustal movements along fault zones
Other evidence indicates that parts of the Earth’s crust have been moving to different locations for billions of years.
Describe pieces of evidence that suggest minor changes in the Earth’s crust.
Displaced & Deformed Rock Strata
Sedimentary rocks appear to form in horizontal layers. However, observations of the Earth’s surface indicate that the original formations of rock have changed through past movements.
Tilting
Earth movement resulting in a change in the position of rock layers, “rocks at an angle”
Folded Strata
Bend in the rock layers produced during the mountain building process
Faulting
Movement of rock along a crack (fault) in the crust
Displaced Fossils
Displaced means “moved.”
Marine fossils- remains or imprints of once living ocean organisms such as coral, fish, etc. found in sedimentary rock
Marine fossils found in layers of sedimentary rock in mountains, often thousands of feet above sea level.
These marine fossils found at high elevation suggest past uplift of rock strata.
Sinking or settling of rock strata
Rock layers that have been moved.
Horizontal Displacement (Faulting)
Earth shifts sideways along a transform fault in the crust
Vertical Displacement (Faulting)
Portion of Earth’s surface is either uplifted or subsides along a fault or crack.
Benchmark
Permanent cement or brass marker in ground indicating a measured elevation. Isostasy
Condition of balance or equilibrium in Earth’s crust.
Since the upper mantle acts like a very dense fluid, the crustal plates float on top of it.
Any change in one part of the crust is offset by a corresponding change in another part of the crust.
Example of Isostasy