Theory
- an idea that is used to explain observed facts.
(Unnamed Theory) 1908
frank B. Taylor ( 1860-1939 )
- an American geologist
- suggested that the Earth had not shrunk. He said that the continents formed from 2 large continents, one located over each pole. These continents broke apart in a ''creeping'' motion. No one really believed Taylor's idea and most scientists just ignored it.
Mohorovicic Discontinuity/Moho (1909)
Andrija Mohorovicic (1857-1936)
-Croatian scientist
-discovered that the speed of seismic waves increases abruptly by 32-64 km beneath the Earth's surface.
This change in the speed of the waves marks the boundary between the crust and the mantle. This boundary is called the Mohorovicic Discontinuity or Moho.
Continental Drift Theory (1912)
Alfred B. Wegener (1880-1930)
-German scientist
-claimed that the continents once formed part of a single landmass, which he named Pangaea, meaning ''all lands.'' Surrounding Pangaea was a huge ocean called Panthalassa meaning ''all seas.''
According to Wegener, about 200 million years ago, Pangaea began breaking up into smaller continents, which drifted to their present locations. He speculated that this motion may have crumpled the Earth's crust in places, thus producing mountain ranges.
Pieces of Evidence: the way that South America fits with Africa. The same kinds of plant and animal fossils were also found in both places. Despite these pieces of evidences, scientists did not agree with him. The reason was because he could not explain why or how continents moved.
Wegener spent the rest of his life searching for evidence to prove his theory. He died 1930 without convincingly explaining what caused continents moved.
Seafloor Spreading ( 1960)
- hot molten rock was flowing up through cracks in the floor of the Atlantic Ocean.
>Molten rock flowing from the crack formed the mountains.
As the molten rock hardened, it pushed older ocean floor apart ----> Seafloor Spreading.
Plate Tectonic Theory
tectonic - ''builder''
-this theory suggest that the crust of the Earth is made up of number of large rigid plates and a number of smaller ones. Most of the plates are named for the continents that rest them.
12 major plates and 38 minor plates have been identified.
Plates with continents move relatively slow. They move about 2cm each year. Those without continents move faster, about as much as 12 cm per year.
- an idea that is used to explain observed facts.
(Unnamed Theory) 1908
frank B. Taylor ( 1860-1939 )
- an American geologist
- suggested that the Earth had not shrunk. He said that the continents formed from 2 large continents, one located over each pole. These continents broke apart in a ''creeping'' motion. No one really believed Taylor's idea and most scientists just ignored it.
Mohorovicic Discontinuity/Moho (1909)
Andrija Mohorovicic (1857-1936)
-Croatian scientist
-discovered that the speed of seismic waves increases abruptly by 32-64 km beneath the Earth's surface.
This change in the speed of the waves marks the boundary between the crust and the mantle. This boundary is called the Mohorovicic Discontinuity or Moho.
Continental Drift Theory (1912)
Alfred B. Wegener (1880-1930)
-German scientist
-claimed that the continents once formed part of a single landmass, which he named Pangaea, meaning ''all lands.'' Surrounding Pangaea was a huge ocean called Panthalassa meaning ''all seas.''
According to Wegener, about 200 million years ago, Pangaea began breaking up into smaller continents, which drifted to their present locations. He speculated that this motion may have crumpled the Earth's crust in places, thus producing mountain ranges.
Pieces of Evidence: the way that South America fits with Africa. The same kinds of plant and animal fossils were also found in both places. Despite these pieces of evidences, scientists did not agree with him. The reason was because he could not explain why or how continents moved.
Wegener spent the rest of his life searching for evidence to prove his theory. He died 1930 without convincingly explaining what caused continents moved.
Seafloor Spreading ( 1960)
- hot molten rock was flowing up through cracks in the floor of the Atlantic Ocean.
>Molten rock flowing from the crack formed the mountains.
As the molten rock hardened, it pushed older ocean floor apart ----> Seafloor Spreading.
Plate Tectonic Theory
tectonic - ''builder''
-this theory suggest that the crust of the Earth is made up of number of large rigid plates and a number of smaller ones. Most of the plates are named for the continents that rest them.
12 major plates and 38 minor plates have been identified.
Plates with continents move relatively slow. They move about 2cm each year. Those without continents move faster, about as much as 12 cm per year.
