Natural disasters Flashcards
List the parts of the earths layers
Crust: The outermost layer, composed of solid rock. It is thinner under oceans (oceanic crust) and thicker under continents (continental crust).
Mantle: A thick layer of semi-solid rock beneath the crust. It is involved in convection currents that drive plate movement.
Outer Core: A layer of liquid iron and nickel below the mantle. It is responsible for the Earth’s magnetic field.
Inner Core: The innermost layer, made of solid iron and nickel, extremely hot and under high pressure.
Alfred Wegener’s Theory of Continental Drift
Alfred Wegener proposed the Theory of Continental Drift in the early 20th century. According to this theory:
Continents were once part of a single supercontinent called Pangaea.
Over millions of years, Pangaea broke apart, and the continents drifted to their current positions.
Wegener used evidence from fossils, rock formations, and the shape of continents (such as South America and Africa fitting together) to support his theory. However, he couldn’t explain the mechanism behind the drift, which was later understood through the theory of plate tectonics.
Theory of Plate Tectonics
The Theory of Plate Tectonics builds on Wegener’s ideas and explains the movement of Earth’s lithosphere (the crust and upper mantle). It suggests:
The lithosphere is broken into several large and small tectonic plates that float on the semi-fluid asthenosphere below.
These plates move due to convection currents in the mantle, driven by heat from the Earth’s core.
Plate movement causes geological features like mountains, volcanoes, earthquakes, and ocean trenches.
Identify & Compare Divergent, Convergent, and Transform Boundaries
Divergent Boundaries:
Plates move away from each other.
This often occurs at mid-ocean ridges where new crust is created as magma rises to the surface.
Example: The Mid-Atlantic Ridge.
Convergent Boundaries:
Plates move towards each other.
This can result in one plate being forced beneath another (subduction), forming mountains or deep ocean trenches.
Example: The Himalayas (continental-continental convergence) or the Mariana Trench (oceanic-continental convergence).
Transform Boundaries:
Plates slide past each other horizontally.
This causes frequent earthquakes due to the friction between the plates.
Example: The San Andreas Fault in California.
How Subduction Zones Form
A subduction zone forms at convergent boundaries where one tectonic plate is forced under another. This typically occurs when:
An oceanic plate collides with a continental plate (since oceanic crust is denser, it is subducted beneath the lighter continental crust).
The subducting plate is pushed into the mantle, where it melts and forms volcanic activity, deep ocean trenches, and mountain chains.
Example: The Ring of Fire around the Pacific Ocean is a major subduction zone, with volcanic islands and earthquakes.
Draw a diagram of the plate boundaries along the world
https://docs.google.com/presentation/d/1N9OY7FC7r8oxuhmzIvqTybMV8t13CwAImhBMtNBQnq4/edit?pli=1#slide=id.g30f82614674_0_991
What is a convection current
Convection currents transfer heat from one place to another by mass motion of a fluid such as water, air or molten rock.
Who was alfred wegner
Alfred Lothar Wegener was a German meteorologist and geophysicist who is best known for developing the theory of continental drift. His theory, proposed in 1912, suggested that the continents were once joined together in a single supercontinent called Pangaea and have since drifted apart to their current positions.
wegners theory
Wegener’s theory of continental drift proposed that the continents were not stationary, but instead had moved across the Earth’s surface over geological time. He believed that Pangaea existed about 200 million years ago, and through the process of continental drift, it gradually broke apart, with the continents drifting into their present-day positions.
Explanation for the Shapes of the Continents Fitting Together
Wegener observed that the coastlines of continents such as South America and Africa seemed to fit together like pieces of a jigsaw puzzle. He used this as one piece of evidence to suggest that these continents were once part of a larger landmass that had since split apart. The similarity in geological features and fossil evidence across distant continents also supported this idea.
Changes in Wegener’s Idea of Drifting Continents
Wegener’s idea was initially met with skepticism because he could not explain how or why the continents moved. His hypothesis lacked a mechanism for the movement of the continents. Over time, his theory was refined as more evidence emerged, especially after the development of the theory of plate tectonics in the 1960s.
Why Scientists Believe the Crust is Broken Up into Plates
Scientists believe that the Earth’s crust is broken into plates (tectonic plates) because of several key observations:
Seafloor Spreading: The discovery of mid-ocean ridges and the process of seafloor spreading, where new crust forms at ridges and pushes older crust away, supported the idea that continents are part of larger moving plates.
