Unit 7: Earth's Changing Surface Flashcards
Continental Crust vs. Oceanic Crust
Continetal: older, thicker, more dense, made of granite
Oceanic: younger, thinner, less dense, made of basalt
Layers of Earth (surface to deepest)
Crust, Lithosphere, Asthenosphere, Mantle, Outer Core, Inner Core
Continental Drift Theory
- created by Alfred Wegner
- proposed that all of Earth’s landmasses were once joined together
- once a supercontinent (Pangea) that drifted apart
Evidences for Continental Drift Theory
Shape - noticed the continents fit together
Fossils - same species fossils were found on different continents
Climate - tropical plant fossils near the Artic Ocean
Rock Layers - mountain ranges across continents had same rock types + rock layers
Mid Ocean Ridges - Evidence for Plate Tectonic Theory
In the 1920s, Marie Tharp and her husband started researching the ocean floor. They noticed that the ocean floor seemed to be stitched together due to mid-ocean ridges.
Seafloor Spreading
the process in which new ocean floor is created when two tectonic plates move apart.
when plates move apart, magma is able to seep through the cracks in the ocean floor, cool at the surface, and form new land over time.
Cause of Tectonic Plate Movement
convection currents in the mantle cause plates to move towards each other (convergent), away from each other (divergent), or slide past each other
convection occurs due to the cycling of the hot and cool magma
Overview of Plate Boundaries
different types are convergent, divergent, and transform
seismic activity (earthquakes) and volcanic activity happens mostly along plate boundaries
Convergent Plate Boundaries
- tectonic plates move towards each other or collide
- compression force (the crust in the subduction zone is destroyed)
- continental/continental –> folded mountains
- oceanic/continental –> ocean trenches + volcanic mountain ranges
- oceanic/oceanic –> ocean trenches + island arcs
SUBDUCTION - when an oceanic and continental collide, the oceanic goes underneath the continental and volcanic activity occurs on the continental
Divergent Plate Boundaries
- tectonic plates move away from each other (divide)
- tension force (crust is created at plate boundaries)
- continental/continental –> rift valley
- oceanic/oceanic –> mid-ocean ridges
SEAFLOOR SPREADING - explained in another flashcard
Transform Plate Boundaries
- tectonic plates slide past each other
- shearing or friction force (crust is not created nor destroyed)
- continental/continental –> strike-slip fault line
HOT SPOT VOLCANOES - volcanoes that form at unusually hot places called magma plumes where the magma pushes through the crust
Topographic Map Overview
a two-dimensional map or model of the Earth’s surface that shows the elevation of an area
can document change of elevation in an area over time + contour lines represent elevation above sea level
Contour Lines
lines that connect equal lines of elevation on a topographic map + show the shape of the terrain
Contour Interval
the difference in elevation between each line
the numbering from line to line must be constant
Contour Lines Rules
- contour lines never cross each other
- form closed loops
