s3 Flashcards
the thermal energy that was generated during the formation and early evolution of the Earth.
Primordial Heat from Planetary Formation
The process of planet formation involves the collision and aggregation of smaller bodies (planetesimals). The kinetic energy from these collisions was converted into heat.
Accretion
As the Earth formed, gravitational forces caused it to compress. The conversion of gravitational potential energy into thermal energy generated significant heat.
Gravitational Compression
The decay of short-lived radioactive isotopes (such as aluminum-26) during the early stages of Earth’s formation contributed to the initial heat.
Radioactive Decay
also known as gravitational contraction or self-compression, is the process by which a celestial body generates heat due to the conversion of gravitational potential energy into thermal energy.
Process converting gravitational potential energy into thermal energy during celestial body formation.
Gravitational Compression
Accretion of smaller bodies into a larger body increases mass and gravitational force.
Formation Process
The potential energy of particles transforms into thermal energy through friction and collisions.
Conversion of Energy
Generated by the movement of tectonic plates.
Heat from Friction Due to Plate Movements
Significant heat produced in the planet’s interior during early formation stages.
Heat Generation
Plates of the Earth’s crust move over the semi-fluid asthenosphere.
Tectonic Activity
Plates grinding against each other at boundaries (convergent, divergent, and transform) generate frictional heat
Frictional Heat
Heat generated within the Earth’s interior is transferred to the surface through three main mechanisms: conduction, convection, and radiation.
Heat Transfer Mechanisms within Earth
One plate being forced under another generates significant friction and heat.
Subduction Zones
Direct Heat Transfer: Heat moves through solid materials like rocks.
Conduction
Fluid Movement: Heat transfer through the movement of semi-fluid rock in the mantle.
Convection
Localized Heat Sources: Areas of volcanic activity not directly associated with plate boundaries
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Hotspots
- Heat
- Pressure
- Volatiles
Conditions Required for Magma Formation
For rocks to melt and form magma, temperatures must be high enough to overcome the bonds holding the minerals together.
Heat
Residual heat from the planet’s formation.
Primordial Heat
Continuous heat production from the decay of radioactive isotopes.
Radioactive Decay
Generated by the movement and deformation of tectonic plates.
Frictional Heating
- Decompression Melting
- Flux Melting
- Heat-Induced Melting
Processes Leading to Magma Formation
Heat-induced melting occurs when the temperature of the mantle or crust increases due to tectonic processes such as mantle plumes or hotspots.
Heat-Induced Melting
Occurs when there is a decrease in pressure as mantle rocks ascend. This process is common at divergent plate boundaries, such as mid-ocean ridges, where tectonic plates move apart. As the pressure decreases, the mantle material rises and partially melts, forming basaltic magma.
Decompression Melting
Happens when volatiles like water and carbon dioxide are added to the mantle, reducing the melting temperature of the rocks.
Flux Melting
these chambers act as storage areas where magma can evolve before potentially leading to volcanic eruptions.
Magma Chambers
When magma cools and solidifies below the Earth’s surface, it forms intrusive igneous rocks.
Intrusive Pathways
Low in silica (about 45-55%) and high in iron and magnesium, basaltic magma is the most fluid type. It commonly forms shield volcanoes and basalt plateaus
Basaltic Magma
When magma reaches the surface, it erupts through volcanic vents, forming extrusive igneous rocks like basalt, andesite, and rhyolite.
Extrusive Pathways
Intermediate in silica content (about 55-65%), andesitic magma is more viscous than basaltic magma. It is often associated with stratovolcanoes and volcanic arcs
Andesitic Magma
Low-viscosity magma (typically basaltic) flows out of the volcano, forming lava flows. These eruptions are generally less explosive and create broad gently sloping shield volcanoes.
Effusive Eruptions
High-viscosity magma (such as andesitic or rhyolitic) traps gases, leading to pressure build-up and explosive eruptions. These eruptions can produce pyroclastic flows, ash falls, and significant volcanic debris, forming steep-sided stratovolcanoes or calderas
Explosive Eruptions:
Formed by low-viscosity basaltic lava that flows easily and spreads widely
Shield Volcanoes
Characterized by alternating layers of lava and pyroclastic material, resulting from explosive and effusive eruptions.
Stratovolcanoes/composite:
Large, basin-shaped depressions formed when a volcano collapses following a massive eruption.
Calderas
As magma cools, early-forming minerals crystallize and settle out of the melt, removing specific elements and altering the composition of the remaining liquid. This process can create layered intrusions with distinct mineral bands
Fractional Crystallization
Magma can incorporate surrounding rock material as it ascends, altering its composition. This process is called assimilation, and it can lead to the formation of hybrid magmas with mixed characteristics.
Assimilation
When magmas from different sources or depths come into contact, they can mix, forming a new magma with intermediate properties. This process can produce complex igneous rock formations with varied textures and compositions.
Magma Mixing
Caused by mechanical deformation along fault zones, leading to changes primarily due to pressure. This can create rocks like mylonite.
Dynamic Metamorphism
