Plate Tectonics Flashcards
What are the 4 Layers of the Earths Crust
Crust, Mantle, Outer Core, Inner Core
What is the composition of the Crust
Thin brittle layer that consists of the:
Continental Crust
Thicker (10 - 70km)
Rich in silicates and aluminium minerals
Oceanic Crust
Thin ( 5km), more dense and similar composition to basalt
Rich in Magnesium and silicate minerals
What is the composition of the Mantle
Thickest layer of the earth (Average 2900 km thick)
Molten rock with convection currents in the upper mantle
High temperature and pressure
is primarily composed of silicate minerals rich in iron and magnesium
What is the composition of the Outer Core
Liquid
Iron, Nickel and some lighter elements
Convection currents in the outer core may be responsible for the earth’s magnetic field
What is the composition of the Inner Core
Solid due to high temperatures and pressures.
Mostly Iron with some Nickel
What is evidence for the Continental Drift Theory
Fit of coastlines, similar fossils on separate continents, and the presence of ancient climate indicators similarities in rock formations and mountain ranges across continents, earthquake and volcano distributions align with plate boundaries, providing evidence for the movement and interaction of tectonic plates.
What is the Continental Drift Theory
A proposed theory that the continents were once united into a single supercontinent named Pangaea. Suggests that that Pangaea broke up and moved long ago and this movement was driven by the gradual motion of tectonic plates on the Earth’s surface.
What is evidence supporting the theory of plate tectonics
Evidence for plate tectonics: Continent fit, rock/fossil matches, seismic activity, earthquake/volcano patterns at plate boundaries, oceanic features (ridges, trenches).
How does the location of earthquakes and volcanoes support the theory of plate tectonics
Earthquakes occur at plate boundaries due to plate interactions, like subduction or sliding.
Volcanoes emerge where plates separate or collide, allowing molten material to surface.
Divergent boundaries show volcanic activity and shallow quakes.
Convergent boundaries yield deep earthquakes.
Transform boundaries cause shallow but powerful quakes.
The consistent alignment of earthquake and volcanic activity with the locations of tectonic plate boundaries and their interactions provides strong evidence for the theory of plate tectonics.
Why can volcanoes be found in the middle of a tectonic plate even if they are not on plate boundaries
volcanoes result from hotspots where magma rises through the plate from deep within the Earth, leading to volcanic activity even in the middle of tectonic plates.
Why can earthquakes be found even if they are not on plate boundaries
Known as intraplate earthquakes, these earthquakes occur due to stress accumulation in weak zones within the Earth’s crust, resulting in sudden energy release despite not being directly associated with tectonic plate interactions.
Explain why plate tectonics move in terms of heat and convection currents
Tectonic plates move due to heat-driven convection currents in the mantle. Hot, less dense mantle material rises and pushes plates apart at divergent boundaries, while cooler, denser material sinking drives plates together at convergent boundaries.
Describe the process of subduction
Subduction is the process where a denser oceanic plate is pushed beneath a less dense plate at a convergent boundary. This leads to the formation of deep ocean trenches, volcanic arcs, and the recycling of Earth’s crust over long periods of time.
How are ocean ridges formed?
Ocean ridges form where tectonic plates move apart. Hot mantle material rises through stretched crust, making magma. Magma erupts, cools, and forms new crust, building underwater mountain ranges. This process is seafloor spreading.
Describe the theory of Seafloor Spreading and how it supports plate tectonics.
Seafloor spreading is a key part of plate tectonics. Hot mantle material rises at divergent boundaries, making magma that erupts, cools, and forms new seafloor. As this new crust forms, it pushes older crust away. This process helps explain the movement of tectonic plates and the creation of ocean ridges.
What are the three types of plate boundaries
Divergent, Convergent and Transform
Describe the characteristics and give examples of transform boundaries
These boundaries involve plates sliding past each other horizontally. The friction between the plates creates stress that’s eventually released as earthquakes. No new crust is created or destroyed at transform boundaries; no volcanoes.
San andreas fault
Describe the characteristics and give examples of convergent boundaries
At these boundaries, plates move toward each other. Depending on the types of plates involved (oceanic or continental), one plate may be forced beneath the other in a process called subduction. This can lead to the formation of deep ocean trenches, volcanic arcs, and mountain ranges.
Describe the characteristics and give examples of divergent boundaries
Here, tectonic plates move away from each other. Characterized by the formation of new crust as magma rises from the mantle to fill the gap, creating new crust. This process forms mid-ocean ridges and contributes to seafloor spreading. Examples:
Mid-Atlantic Ridge
Great Rift Valley
Red Sea Rift
Iceland
Explain what a hot spot is and it’s significance
is an area of intense volcanic activity caused by a rising column of hot mantle material. It creates volcanic islands and chains away from plate boundaries, like the Hawaiian Islands, and offers insights into plate movement and the Earth’s internal dynamics.
Describe the difference between continental and oceanic crust
Continental crust is thicker (Between 30 - 70km), less dense, and composed mainly of granite and sedimentary rocks. It forms the continents and is more stable. Oceanic crust is thinner (Avg 6 km thick), denser, and composed mainly of basalt. It forms the ocean floors and is more geologically active.
Explain how palaeomagnetism can be used to support the theory of Seafloor Spreading.
Palaeomagnetism reveals Earth’s magnetic past in rocks. As new crust forms at mid-ocean ridges, rock minerals align with the magnetic field. Flips in Earth’s field create bands of normal/reversed polarity. Symmetrical magnetic patterns on both sides of ridges confirm plate movement and seafloor spreading theory.
What is the shrinking Earth Theory and what predictions does it make about the locations of mountains, volcanoes and earthquake
The shrinking Earth theory suggests that our planet was once much larger and has been gradually contracting over time. This theory proposes that as the Earth shrinks, it causes the crust to buckle and fold, leading to the formation of mountains, volcanoes, and earthquakes.
What is the Name of the scientist responsible for the Continental Drift Theory
Alfred Wegener
Define Pangea
Pangaea was a vast supercontinent existing about 335 million years ago, comprising all the current continents fused together. Over time, tectonic forces led to its fragmentation into the continents we know today.
Define Gondwana
Gondwana: Ancient southern supercontinent (around 335 million years ago) including present-day South America, Africa, Antarctica, Australia, Indian subcontinent, and Arabian Peninsula; later split into current continents.
Define Laurasia
Laurasia was a northern supercontinent that existed around 335 million years ago, incorporating present-day North America, Europe, and Asia
Define Panthalassa
Panthalassa was the vast global ocean that surrounded the supercontinent Pangaea during the late Paleozoic and early Mesozoic eras. It encompassed most of Earth’s oceanic area at that time and existed approximately 335 to 175 million years ago.
What is a subduction zone
A subduction zone is where one tectonic plate sinks beneath another due to convergence. It causes geological activity like earthquakes, volcanoes, and mountain formation. Typically involves oceanic plates and generates features such as trenches and volcanic arcs.
Characteristics of Convergent Boundaries (Continent to Continent)
Produce lots of earthquakes
Very little volcanoes
Continental Crust on both sides is light and resists subduction
Mountain Building
Characteristics of Convergent Boundaries (Oceanic to Continent)
Subduction Zone Formation
Explosive Volcanic Activity
Earthquakes
Formation of Mountain Range
Characteristics of Convergent Boundaries (Oceanic to Oceanic)
Subduction Zone Formation
Trench Formation
Explosive Volcanism
Earthquakes
