Tectónica de Placas - Parte II

Summary

The transcript explores the scientific theories behind the movement of continents, focusing on the concept of plate tectonics. It covers the contributions of Arthur Holmes, who first proposed convection currents in the mantle, and Dan McKenzie and Jens Morgan's development of the plate tectonics model in 1968. The theory suggests that Earth's lithospheric plates float on a ductile, viscous layer of the mantle, driven by convection currents. It delves into the types of plate boundaries—divergent, convergent, and transform—explaining their geological effects such as earthquakes, volcanic activity, and mountain formation.

Takeaways

• 😀 Arthur Holmes first proposed the existence of convection currents in the Earth's mantle in 1928, suggesting a mechanism for the movement of continents.
• 🌍 The heat from Earth's internal radioactivity causes the mantle material to heat up, rise, and then cool, leading to lateral movement of the continents.
• 🌋 The movement of tectonic plates, and consequently the continents, is driven by convection currents in the Earth's mantle.
• 🌐 The Earth's surface is divided into tectonic plates, including continental and oceanic crust, which float atop the mantle's ductile layer called the asthenosphere.
• 🔍 The discovery of earthquake and volcano distributions helped validate the theory of plate tectonics, showing their clustering along plate boundaries.
• 🪐 The lithosphere is broken into large tectonic plates that move across the asthenosphere, and this movement is influenced by subduction zones and convection currents.
• 💥 The theory of plate tectonics was further developed by Dan Peter McKen and Jens Morgan in 1968, explaining the dynamics of the lithospheric plates.
• 🗺️ The Earth's lithosphere is divided into seven major plates and several smaller ones, which are in constant motion.
• 🌊 Plate movements can result in geological phenomena such as earthquakes, volcanic eruptions, and mountain formation, especially at plate boundaries.
• ⚡ Plate boundaries can be divergent (plates move apart), convergent (plates collide), or transform (plates slide past each other), each causing different geological activities.

Q & A

What was Arthur Holmes' contribution to the theory of plate tectonics in 1928?

In 1928, Arthur Holmes proposed the existence of convection currents in the Earth's mantle. He suggested that these convection currents could cause the lateral movement of continents, with heat from the Earth's interior driving the movement of mantle material.

What is the mechanism of convection currents in the mantle as described by Holmes?

Holmes described convection currents as the movement of material in the mantle caused by internal heat from the Earth's core. As the material heats up, it rises to the surface, and as it cools, it sinks again, creating a cycle that drives the movement of tectonic plates.

How do plate tectonics explain the movement of continents?

Plate tectonics explains that continents move because the Earth's lithosphere is divided into large plates that float atop the asthenosphere. Convection currents in the mantle cause these plates to move, leading to the shifting of continents over time.

What role do subduction zones play in plate tectonics?

Subduction zones are areas where one tectonic plate is forced beneath another, causing the destruction of lithosphere and contributing to geological phenomena like volcanic activity, earthquakes, and mountain formation.

What evidence supports the theory of plate tectonics?

Evidence for plate tectonics includes the mapping of earthquake and volcano locations, which are not randomly distributed but instead occur along specific lines that correspond to the boundaries of tectonic plates.

What is the structure of the Earth's interior according to the theory of plate tectonics?

According to plate tectonics, the Earth is made up of several layers: the lithosphere, consisting of the oceanic and continental crust and the upper mantle; the asthenosphere, a ductile, hot layer that allows the lithosphere to move; and deeper layers like the mesosphere, outer core, and inner core.

What distinguishes the three types of plate boundaries?

The three types of plate boundaries are divergent (plates move away from each other), convergent (plates collide), and transform (plates slide past one another). These boundaries result in different geological activities like earthquakes, volcanism, and mountain building.

What happens at divergent plate boundaries?

At divergent boundaries, two tectonic plates move away from each other, often creating new oceanic crust through the upwelling of magma. This process can also lead to the formation of rift valleys on continents.

How do convergent boundaries lead to the formation of mountains?

At convergent boundaries, two plates collide. If both are continental plates, the collision leads to the folding and uplifting of the crust, forming mountain ranges, such as the Himalayas, resulting from the collision of the Indian-Australian and Eurasian plates.

What is the significance of transform boundaries, such as the San Andreas Fault?

Transform boundaries, where plates slide past each other, often cause significant earthquakes due to the friction between the plates. The San Andreas Fault in California is a well-known example, where tectonic movement can lead to major seismic activity.