Inside Earth Flashcards
What are seismic waves?
They are special vibrations that travel through the Earth. They have revealed the structure of the Earth interior. They are caused by events like Earthquakes and human made blasts. A seismologist is a person who detects and interprets these vibrations.
What is up and down wave motion?
Motion that makes the wave go up and down. Like waves in a pool
What is side to side wave motion?
Motion that goes side to side. Like wiggling a rope.
What are P-Waves?
P waves are short for primary waves. They travel faster than S-waves. P waves travel through solids and liquids. They are in a front and back motion (longitudinal waves)
What are S-waves?
P-waves is short for secondary waves. They a travel slower than p-waves. Slower S-waves travel with a side to side motion (transverse waves). They don’t pass through liquids. This is how scientists got to know that the outer core is liquid. The S-wave shadow zone is area where the waves can’t be detected.
What are the 3 simple layers of the Earth
- Crust
- Mantle
- Core
What is the crust?
It is the outermost layer of the Earth. Oceanic crust lies under oceans and is thin (about 5 km). Continental crust forms continents and is thicker (about 30 km). Because the rock in the crust is cool, the crust is brittle and shallow earthquakes occur here. The crust floats on the mantle.
What is the mantle?
The mantle is the thick layer between the crust and the core. It is about 2900 km thick. It includes the upper mantle, asthenosphere and then the lower mantle. The lithosphere consists of the curst and the upper mantle.
What is the lithosphere?
The lithosphere includes the crust and the upper mantle. The plates that move about earth’s surface are pieces of the lithosphere.
What is the asthenosphere?
It lies just beneath the lithosphere, the lithosphere floats on it. It is a soft weak zone of hot rock where temperatures and pressure case the mantle rock to me more fluid than anywhere else in the mantle.
What is the lower mantle?
It is about 660 to 2900 km deep. It is the largest part of the Earth’s interior. It is under great pressure and the tock found there gradually becomes rigid with depth. Despite its rigidity the rock of the lower mantle is very hot and flows slowly.
What is the outer core?
It is liquid. It is made mostly of iron. Powerful electric currents are formed as the liquid moves. These currents make the Earths magnetic field. The magnetic field protects us from harmful solar radiation. It also protects the atmosphere. It helps life on earth survive.
What is the inner core?
It is mode mostly of iron. It is solid and not melted because melting depends on pressure as well as temperature. The pressure in the inner core is so much that it remains solid.
How does convection occur in the lower mantle?
The hot core heats the lower mantle where two layers meet. Heating causes the material to expand making it less dense, the less dense objects then float to the top getting replaced by objects with higher density.
What are convections cells?
The convection current moves along under the lithosphere. Eventually it loses it heat and sinks back to the core. This is a convection cell.
What is Seismic tomography?
It uses seismic waves collected from all over the world to create a computer generated three dimensional imagine of the earths interior.
What is the IODP
Integrated Ocean Drilling program. Their goal is to
break into the upper mantle. They are looking for a boundary called Moho (Mohorovicic Discontinuity) located between the Earths crust and the upper mantle
What is the Moho?
Moho (Mohorovicic discontinuity) is the boundary between Earths crust and the upper mantle. Named after Andrija Mohorovicic, the Croatian seismologist who first identified it in 1909.
Is the Earths core spinning?
Scientists think that the earths core is spinning (outer core), and that too faster than the earths rotation on its axis. This is because they studied two P-waves send during Earthquakes that occurred in the same area. If the Core was spinning at the same speed at Earths rotational axis, the time taken to record would the same. But they were different, meaning that the waves in the same area passed through different parts of the core. The core actually laps the surface every 400 years.
What is continental drift?
It is the idea that continents move around on Earth’s Surface. Suggested by Alfred Wegener.
What is Pangaea?
It is an ancient, huge landmass composed of earlier forms of today’s continents. It is an ancient supercontinent. Suggest by Wegener
What are plate tectonics
It is a theory explaining how the pieces of Earth’s surface (The plates) move. It is the study of tectonic plates
What was the evidence for continental drift?
- Coal beds stretch across the US till Europe.
- Matching Plant fossils in South America, Africa, Antartica, India and Australia
- Matching fossils in South America and Africa
- Evidence of glaciers that were present in warm dry climates. This indicates that continents in tropical regions currently were once close to the south pole
What are mid-ocean ridges?
They are long chains of undersea mountains. New ocean floor forms here
What is the seafloor spreading hypothesis?
It is a hypothesis that new sea floor is created at mid-ocean ridges and that, in the process, the continents are pushed apart from each other.
What evidence suppports the sea floor spreading hypothesis?
- Magnetic reversal patterns - Striped patterns form as magnetic minerals in new rock align to earths magnetic fields. Magnetic patterns matched on both sides of the ridges.
- Oldest rock was furthest from the ridge, meaning that the new rock created at the ridge pushed the old rock away from it.
What are tectonic plates?
They are large pieces of Earths Lithosphere that move over the asthenosphere
What are Oceanic plates?
They are thin tectonic plates that are made of basalt and form the ocean floor. They are denser than continental plates
What are continental plates?
They are thick tectonic plates that are mode of andesite and granite and form the continents. They are less dense than oceanic plates.
What happens at mid ocean ridges?
As the less dense rock rises up due to convection, the plates move apart making room. Basaltic lava at mid ocean ridges is spread between the gap of the plates, the lava cools down to make the tectonic plates bigger.
What is mantle plume?
It is the heated lower mantle rock that rises toward the lithosphere because it is less dense than the surrounding rock.
How are islands formed?
When a hot mantle plume causes a volcanic eruption in the plate above it, it may form an island. After the island forms the movement of the plate carries it away from the mantle. Without the heat from the mantle plume the volcano that formed the island becomes dormant.
