Tectonic Plates—What are the lithospheric plates? (Educational)

00:06:40
https://www.youtube.com/watch?v=Xzpk9110Lyw

Resumo

TLDRThe video provides an overview of the Earth's lithosphere, which consists of tectonic plates that are in constant motion. It explains the structure of the lithosphere, including the mantle and the differences between continental and oceanic lithosphere. The video categorizes plate interactions into three main types: transform, divergent, and convergent boundaries, detailing how these interactions lead to geological phenomena such as earthquakes and volcanic activity. It emphasizes that most tectonic activity occurs at plate boundaries, where various geological features are formed.

Conclusões

  • 🌍 The lithosphere is the Earth's outer layer, divided into tectonic plates.
  • 🔄 Tectonic plates move and interact through plate tectonics.
  • 🌊 Oceanic lithosphere is denser and thinner than continental lithosphere.
  • ⚡ Earthquakes primarily occur at plate boundaries due to rock fractures.
  • 🔺 Convergent boundaries can lead to subduction and large earthquakes.
  • 🌋 Divergent boundaries create new oceanic crust at spreading ridges.
  • 🗻 Continental collisions produce mountains and plateaus.
  • 📉 Transform boundaries involve horizontal movement of plates.
  • 🌊 Island arcs form from volcanic activity at subduction zones.
  • 📏 Continental lithosphere ranges from 150 to 200 km thick.

Linha do tempo

  • 00:00:00 - 00:06:40

    The lithosphere, Earth's outer layer, consists of major and minor tectonic plates in constant motion due to plate tectonics. These plates can be entirely oceanic or a mix of oceanic and continental lithosphere. The Earth's interior includes the mantle, a thick rock layer composed of high-magnesium silicate, with the lithospheric mantle being cooler and more rigid than the deeper asthenosphere. The lithospheric plates, made of crust and the upper mantle, move as a single unit, causing earthquakes when brittle rock fractures. Continental lithosphere is thicker and more buoyant than oceanic lithosphere, which is denser and forms the ocean floor. Plate interactions are categorized into three types: Transform, Divergent, and Convergent boundaries, each with distinct geological features and earthquake characteristics. Transform boundaries involve horizontal movement, Divergent boundaries create new oceanic crust, and Convergent boundaries lead to subduction and mountain formation, with the majority of earthquakes occurring near these boundaries.

Mapa mental

Vídeo de perguntas e respostas

  • What is the lithosphere?

    The lithosphere is the cool, rigid outer layer of the Earth, broken into tectonic plates.

  • What are the main types of tectonic plate boundaries?

    The main types are transform, divergent, and convergent boundaries.

  • What is subduction?

    Subduction is the process where one tectonic plate is forced beneath another.

  • How thick is continental lithosphere?

    Continental lithosphere typically ranges from 150 to 200 km thick.

  • What causes earthquakes?

    Earthquakes occur when brittle rock fractures and breaks, primarily at tectonic plate boundaries.

  • What is the difference between oceanic and continental crust?

    Oceanic crust is denser and thinner than continental crust, which is thicker and more buoyant.

  • Where do most earthquakes occur?

    More than 75% of all earthquakes occur on or near convergent boundaries.

  • What is a transform boundary?

    A transform boundary is where plates move horizontally against each other.

  • What happens at divergent boundaries?

    At divergent boundaries, oceanic crust forms as plates pull apart, creating new crust.

  • What is an island arc?

    An island arc is a line of volcanoes that forms on the upper oceanic plate during subduction.

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  • 00:00:10
    The cool, rigid, outer layer of the earth, the lithosphere, is broken into massive plates.
  • 00:00:17
    There are about a dozen major plates and many smaller plates in continuous motion as they
  • 00:00:21
    collide with, slide under, or move past each other in a process known as plate tectonics.
  • 00:00:27
    A plate may be entirely oceanic lithosphere, like the Pacific Plate, or,
  • 00:00:32
    like the NorthAmerican plate can be part oceanic and part continental lithosphere.
  • 00:00:37
    We will return to lithosphere types in a minute, but first, let’s look inside the EArth to
  • 00:00:42
    clarify the layers. The mantle is a 2900 km-thick rock layer between the crust and core. The
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    composition is high-magnesium silicate. The uppermost part, the lithospheric mantle, is
  • 00:00:56
    cooler and more rigid than the deeper mantle. It lies above a hotter and more-ductile layer
  • 00:01:03
    of similar composition called the asthenosphere. As an analogy to how a rock can be either
  • 00:01:08
    brittle or ductile, consider a taffy bar, like the Big Hunk. When force is applied it
  • 00:01:15
    is brittle when cold, and ductile when warm. Zooming in to a tectonic cross section we
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    see that the lithospheric plates are composed of crust on top of the outermost rigid part
  • 00:01:28
    of the mantle. Although the mantle has a different composition and higher density than the crust,
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    these two layers migrate as a single mechanical layer called a lithospheric, or tectonic plate.
  • 00:01:41
    This is where earthquakes occur as brittle rock fractures and breaks. The hotter and
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    more-ductile asthenospheric rock does not fracture to produce earthquakes.
  • 00:01:53
    Continental lithosphere, with continental crust above lithospheric mantle, typically
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    ranges from 150 to 200 km thick. Continental crust stands above sea level because it has
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    an average thickness of 40 km and is mostly more buoyant silica-rich low-density granitic,
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    sedimentary and metamorphic rocks which form the continents.
  • 00:02:17
    OCEANIC lithosphere, formed at spreading ridges, is typically 50–140 km thick. Oceanic crust
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    is only around eight kilometers thick and is denser than continental crust because it
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    contains less low-density silica, and more high-density iron and magnesium. Thus, it
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    forms the ocean floor with its top surface below sea level.
  • 00:02:41
    Relative motion between plates can be broadly grouped into three main categories: Transform,
  • 00:02:47
    Divergent, and Convergent. RETURNING to the world map view, we show.
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    1) Transform, or strike-slip, boundaries: where plates move horizontally against each other,
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    2) Divergent, or constructive, boundaries: where plates move apart from one another, and
  • 00:03:04
    3) Places were plates press into one another are called convergent, or destructive, boundaries.
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    Lithosphere is neither created nor destroyed along transform boundaries which connect segments
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    of spreading oceanic ridges and other plate boundaries. Transform boundaries can also
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    cut across continents as the San Andreas Fault Zone does in California where it connects the East
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    Pacific Rise  to the Cascadia subduction zone. Shallow earthquakes on long transform
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    boundaries that cut continental crust, can approach magnitude 8 whereas those on oceanic
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    transform boundaries tend to be smaller. At divergent boundaries, oceanic crust forms
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    at spreading ridges where plates pull away from each other. A small volume of the mantle
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    melts to create the crust. The hot, buoyant upwelling mantle supports the oceanic ridges
  • 00:03:59
    that forms Earth’s longest mountain systems. Because temperature increases rapidly with
  • 00:04:04
    depth at divergent boundaries, there is only a thin layer of brittle rock to fracture in
  • 00:04:10
    earthquakes. Most earthquakes occur within the upper ten kilometers and have magnitudes
  • 00:04:15
    that are generally less than six. More than 75% of all earthquakes occur on
  • 00:04:22
    or near convergent boundaries. Here, an oceanic plate is forced beneath a continental
  • 00:04:28
    in a process called subduction. Indeed, the world’s largest earthquakes occur near the
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    shallow edge of the boundary where magnitude 9’s have been recorded.. At this location
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    stress builds up over 10’s to 100’s of years until it releases like a spring. and
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    can produce tsunamis. A broad zone of shallow earthquakes occurs within the overriding plate
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    due to compressive forces near the convergent boundary. earthquakes can reach depths of
  • 00:04:57
    700 km within the subducting plates because the oceanic plate can remain cold and brittle
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    as it dives into the deeper mantle. Similar processes occur when an oceanic plate
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    subducts beneath another oceanic plate. Here, an ocean trench marks the location where the
  • 00:05:16
    plate is pushed down into the mantle. In this case, the line of volcanoes that grows on
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    the upper oceanic plate is an island arc. Not all convergent boundaries involve subduction.
  • 00:05:30
    When the continental parts of converging plates come together, neither can subduct. Instead
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    the two continents collide, producing horizontal deformation and uplift of continental crust
  • 00:05:42
    to build mountains and plateaus. Frequent shallow earthquakes in continental collision
  • 00:05:48
    zones can exceed magnitude 8 and are generally less than 40 km deep.
  • 00:05:55
    In addition to these three boundaries, there are also diffuse boundary zones in which deformation
  • 00:06:01
    occurs over a wide region. Although less common than earthquakes along the plate boundaries,
  • 00:06:08
    earthquakes in the interior part of plates, called intraplate earthquakes, do occur.
  • 00:06:15
    Nevertheless, tectonic activity and earthquakes are chiefly concentrated at, or near plate
  • 00:06:21
    boundaries where many geological features including volcanoes, mountains, trenches occur.
Etiquetas
  • lithosphere
  • tectonic plates
  • earthquakes
  • plate boundaries
  • continental crust
  • oceanic crust
  • subduction
  • transform boundaries
  • divergent boundaries
  • convergent boundaries