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.
What are divergent plate boundaries?
Tectonic plate boundary where two tectonic plates move apart. They are at mid ocean ridges, that move apart to make new crust. This boundary is found over a rising convection cell. The rising heat from the convection cell causes the plates the move apart. The plate makes room for it. Then it cools down and becomes a new ocean crust.
They can also be found on continents as rift valleys. When a rift valley forms, it may eventually split enough so that the sea flows into it. This then becomes a mid oceanic ridge. The African rift valley is an example of the rifting process
What are Convergent plate boundaries?
They are places where two tectonic plates come together. When two plates hit each other, the denser plate subducts into the mantle under the less dense one, this creates a valley called a deep ocean trench. When an oceanic plate and a continental plate come together, the oceanic plate being more dense subducts under the continental plate. Once the oceanic plate is completely subducted, two continental plates meet. Since their density is similar, they crash to form mountains. An example of this is the Himalayan mountain range.
What are transform-fault plate boundaries?
This is a tectonic plate boundary where two plates slide past each other. They can be identified by a zigzag pattern from above. They also create earthquakes.
What is a foreshock?
A small burst of shaking that occurs before a large earthquake.
What is a aftershock?
It is a small tremor that occurs before a large earthquake.
What is an earthquake?
It is the movement of Earth’s crust resulting from the release of built up potential energy between two stuck tectonic plates.
What is the focus?
It is the point below Earth’s surface where a rock breaks or slips and causes an earthquake
What is the fault of a earthquake?
A region on Earth’s surface that is broken and where movement occurs.
What is the epicenter of an earthquake?
It is the point right above the focus of an earthquake.
The earthquakes stick-slip motion
Tectonic plates slide past each other. As this happens they may stick to each other due to friction. As a result potential energy builds up and then eventually the plates will slip, releasing energy to form a earthquake. This is called the stick slip motion
How does the frequency of Earthquakes in a place affect its strength?
In places where earthquakes occur frequently they are likely to be mild as little energy is released during each earthquake. These frequent earthquakes release potential energy before it can build up to a high level. On the other hand in places that where earthquakes occur very rarely they are likely to be huge as the long intervals between earthquakes allows a great deal of potential energy to build up.
Can one earthquake trigger other earthquakes?
Yes, one earthquake can trigger other earthquakes. Boundaries of tectonic plates have many sections. When there are two sections, on ahead of the other, both having a lot of potential energy. Then a earthquake occurs in the section in front, the difference in potential energy can cause another earthquake.
Earthquakes in the middle of plates
Tectonic plates are torn apart and joined with other plates. Due to this there are old plate boundaries inside of the plates we see today. When the crust above the bigger plate flexes due to tectonic activity, the smaller older plates that joined with this place can break apart to cause earthquakes.
What is a seismograph?
It is an instrument that measures and records seismic waves.
What are body waves?
Seismic waves that travel through the interior of the Earth. There are two types, P-waves and S-waves.
What are surface waves?
They are seismic waves that reach and travel along the Earth’s surface.
How to locate the epicenter of an earthquake?
To locate the epicenter on an earthquake we have to measure the difference in arrival time between p-waves and s-waves to a station. We need three stations to identify the epicenter. Then we draw a circle around each stations location. The edge of each circle indicates every possible place the earthquake could have occurred. In the three stations a place overlaps, that is the epicenter.
What is the richter scale?
It is a scale that ranks earthquakes according to the size of the seismic waves.
What is the moment magnitude scale?
It is a scale that rates the total energy released in earthquakes.
What is a volcano?
It is an erupting vent through which molten rock and other material reach Earth’s surface, or a mountain built from the products of an eruption.
What is magma?
It is underground melted rock
What is a magma chamber?
It is a location where magma collects inside earth
What is lava?
It is magma that has reached earth’s surface.
What are sills and dikes?
A sill is formed by the sideways movement of magma. A Dike is formed when magma moves upward in a sheet that isn’t straight. If a sill or a dike brakes through the surface, another vent will form.
What is a caldera?
It is the bowl-shaped depression formed by the collapse of a volcano after it has erupted.
What is a resurgent dome?
a mound in the vent of an erupted volcano.
What is a lava lake?
It is a pool of lava that has formed in a caldera
What are the three phases of a volcano?
The three phases of a volcano are,
1. Active
2. Dormant
3. Extinct
What is an active volcano?
It is a volcano that is erupting or that has erupted recently
What is a dormant volcano?
It is a volcano that is not erupting now, but may erupt in the future
What is an extinct volcano?
It is a volcano that no longer erupts and is in the process of eroding.
What is a volcano neck?
Solid remains of magma that filled the conduit of an extinct volcano. The neck is exposed as the volcano erodes.
How is magma formed?
Rock melts to become magma. There have to be certain conditions of the rock to melt. We have to heat the rock to its melting point. Lesser pressure has a lower melting point. Hence rocks just below earths surface at low pressure have low melting points. Another was is when water mixes with the rock. Water comes into the mantle at subduction zones. The water chemically reacts with the rock to make it so that it will require lesser temperature to melt. The melted magma is then less dense than the surrounding rock and makes its way up and may eventually erupt onto the Earth’s surface.
What are mid ocean ridge volcanoes?
At mid ocean ridges hot new crust comes under the sea, this crust is at high temperatures but as it rises the pressure lowers causing it to become magma and erupt underwater at midocean ridges.
What is basaltic magma and how does it create new crust?
Magma at mid ocean ridges is melted basalt. Basaltic magma is runny because of its low silica content. When runny basaltic lava oozes out at mid ocean ridges it hits cold seawater to become new crust. Then the crust cracks to release more basaltic magma and the cycle repeats.
What is the rings of fire?
It is a region of Earth’s plate boundaries where oceanic crust is subducting under other plates; active volcanoes and earthquakes are common here.
What is the volcanic island arc?
It is a series of volcanoes formed at a subduction zone.
Volcanic islands away from plate boundaries
They can form in the middle of oceanic plates. Deep mantle material flows slowly to the surface in a narrow mantle plume. The area of plate situated over the plume is called the hot spot, once the plate moves off the hotspot the volcano becomes extinct.
What is a hotspot?
It is the top of a mantle plume
What are volcanic island chains?
They are a series of volcanoes formed as tectonic plate move over the hotspot.
What is weathering?
It is a chemical surface or mechanical process that breaks rocks into smaller pieces.
What is mechanical weathering?
Mechanical weathering breaks rocks into smaller pieces without changing them chemically. The small pieces are identical in composition to the original rock.
What is chemical weathering?
It occurs when the chemical composition of rock changes. This kind of weathering is rapid in tropical regions where it’s moist and warm. In other regions it is slow.
How does gravity and surface area affect weathering?
Gravity pulls weathered rock to lower places like beaches. Due to this the place that is weathered has a larger surface area. A larger surface area makes weathering occur faster.
Agents of mechanical weathering
- Frost wedging
When it rains or snow melts, water seeps into cracks in rocks. If the temperature drops enough the water will become ice. The crystals will grow and take up more space as when water freezes its molecules move apart. This expansion exerts pressure on rocks making them crack further. - Plants and animals
Some plants grow in unusual places and their roots grow deep into cracks in rock where water collects. The roots slowly grow and further erode the rock. Animals that burrow go through the sediment breaking the rock apart. - Water
Changing conditions of wetness can cause minerals to break down. Running water can also carry rocks, and silt to weather other rocks in the path. - Exfoliation
Exfoliation peels rock layers out on by one. With the topmost layer first, and then the layers below. - Wind
Wind can carry silt and can blow on other rocks to weather them.
Agents of chemical weathering
- Water and minerals
Water can react with minerals to form new elements. - Natural acids
Some rocks react chemically with natural acids in the environment. When water mixes with CO2 from the environment it forms carbonic acid that can dissolve rocks. Plants also produce a substance called tannic acids that dissolves with minerals in rocks tweaking them further. - Oxygen
When iron-containing materials (cars, soil, rock, etc) are oxidized a chemical reaction causes the material to rust. When this happens to rocks it weakens the rock.
What are the factors that affect the rate of weathering?
- Water and climate
Humid and warm climes are suited for chemical weathering. Forst wedging and running water. - Plants and animals
Plants can extend their roots and animals can burrow into rock - Minerals
Minerals react with one and other to weather objects. - Surface area
The greater the surface area compared to its volume the faster it will weather
How is erosion affected by ice?
s glaciers move over Earth’s surface they erode materials from some areas and deposit sediment in other areas. There are two types of glaciers - continental and valley glaciers.
1. Glacial Erosion: If the underlying rock has cracks in it the ice can pull our pieces of rock. Scratching produces large grooves or smaller striations in the rock underneath. The scratching also can wear rock into a fine powder called rock flour.
Effects if Glacial erosion: In mountains, valley glaciers can remove rock from the mountaintops to form large bowls called cirques. When a glacier moves into a stream valley, it erodes rock along the valley sides producing a wider, U-shaped valley. Continental glaciers can scour large lakes and completely remove rock layers
Glacial Deposition: When ice melts at the bottom of a flowing glacier or along its edges, the sediment the ice was carrying gets left behind on the surface. This sediment is called till. Till is a large mixture of different-sized particles ranging from clay to large boulders. When glaciers melt their sediments are deposited in gravel and soil. Sand and gravel deposits laud down by streams are called outwash.
How is erosion affected by gravity?
Gravity pulls everything towards the Earth’s center. When gravity alone causes rock or sediment to move down a slow erosion is called mass movement. There are types of mass movements
1. Creep: Sediments slowly move downhill. Common where freezing occurs. As the ice expands in the soil, it pushes sediments up. Then as soil thaws, the sediments move further down the slope.
Slump: A slump occurs when a mass of rock or sediments moves downhill. Slumps frequently occur on slopes that have been undercut by erosion, such as those above the bases of cliffs that have been eroded by waves.
Rock slides: Dring a rock slide layers of rock break lost from slopes and slide to the bottom. This produces a huge, jumbled pile of rocks at the bottom of the slope. Tock slides can be destructive.
Mudflows: A mudflow is a mass of wet sediment that flows downhill over the ground surface. Some mudflows can be thick and flow slowly downhill at rates of a few meters per day.
How is erosion affected by water?
