Pangaea and Continental Drift

History of Planet Earth

• German scientist Alfred Wegener hypothesized in 1910 that all continents were once a single landmass that drifted apart.
• Continental drift refers to the slow movement of the continents across the Earth's surface.
• Pangaea is the name of the supercontinent suggested by Wegener that existed approximately 300 million years ago.

Evidence of Pangaea - Land Features

• Mountain ranges line up between South America and Africa.
• Coal fields in Europe and North America align.

Evidence of Pangaea - Fossils

• Fossils of freshwater reptiles (Mesosaurus) are found on continents now separated by oceans.

Evidence of Pangaea - Climate

• Fossils of tropical plants are discovered near the Arctic Circle, indicating climate change due to land movement.

Plate Tectonics

• Plate Tectonics is the theory that the crust is divided into tectonic plates moving on the mantle.
• Tectonic plates are large pieces of Earth's crust (lithosphere) that slowly move, separated by cracks.
• The crust is the thin, solid outermost layer of Earth, either continental (landmasses) or oceanic (ocean floors).
• The mantle is the layer of molten material beneath the crust.

Theory of Plate Tectonics

• States that plates are in constant motion, driven by convection currents in the mantle.
• A convection current is a circular motion in a liquid where heat rises and cold sinks.
• Convection currents push out hot molten material and pull in the cold, dense rock during subduction.
• Plates move at boundaries.
• A fault is a break in Earth’s crust where rocks move.

Types of Boundaries

• Divergent Boundary - Plates move apart, creating mid-ocean ridges.
• Convergent Boundary - Plates come together, or converge.
• Oceanic Crust meets Oceanic Crust : The more dense plate slips under the less dense plate
• Oceanic Crust meets Continental Crust : The oceanic sinks and the continental is pushed up creating mountains and volcanos
• Continental Crust meets Continental Crust: Both are squeezed up creating mountain ranges.
• Transform Boundary - Plates slide past each other, like the San Andreas fault.

Sea-Floor Spreading

• Sea-floor spreading is the process where molten material (magma) adds new oceanic crust at mid-ocean ridges.
• Molten material rises, erupts out of the ridge, cools, hardens, and pushes old rock outward.
• Mid-Ocean Ridges are chains of underwater mountains where new ocean floor is produced.
• Mid-ocean ridges span all of Earth's oceans.
• Deep-ocean trenches are deep underwater canyons where the ocean floor sinks back into the mantle.
• Subduction is the process where the ocean floor sinks beneath a deep ocean trench.

Rocks

• Rock - naturally solid made up of a mixture of minerals and other materials
• Granite, for example, is composed of feldspar, quartz, and mica.
• Geologists classify rocks based on their origin.
• Origin - is the way a rock forms
• Rocks are majorly classified into igneous, sedimentary, and metamorphic groups.
• Igneous Rock forms from the cooling of magma or lava.
• Metamorphic Rock forms when a rock is changed by heat, pressure, or chemical reactions.
• Sedimentary Rock forms when small particles of rocks or remains of plants and animals are pressed and cemented together.

The Rock Cycle

• Rock Cycle - series of processes on Earth's surface and in the crust and mantle, changing rocks from one kind to another.
• Metamorphic rock is created through heat and pressure.
• Sedimentary rock is created by weathering, erosion, pressing, and cementing.
• Igneous rock is created by the cooling of magma or lava.