Rocks and weathering Flashcards
Inner core
is a solid nickel and
iron ball, under extreme pressure
and a temperature of up to 6000C
Outer core
is liquid nickel and
iron with high pressure and
temperature.
Mantel
is semi-molten rocks
rich in magnesium and silicon up
to 2900km think.
Crust
is solid rock varying
between 0-70km thick. It is
cracked into plates.
1st Type of Crust
Continental Crust
thicker
(30-70km), Less dense
(“lighter”), Older, main rock
type is granite.
2nd Type of Crust
Oceanic Crust
thinner (5-
10km average), More dense
(“heavier”), younger, Main
rock type is basalt.
Lithosphere
makes up the topmost 100km of the Earth and
includes the upper part of the mantle and the whole crust.
Asthenosphere
is the upper part of the mantle that is semi
molten.
Theory of continental drift
the continental landmasses were “drifting” across the Earth, sometimes plowing through oceans and into each other
Evidence of Plate tectonics
• Fit together like jigsaw pieces
• Fossil remains on one continent
and another
• Evolution of animals, who once
lived together.
• Rock type similarities- the
geological sequence of
sedimentary and igneous rocks in
parts of Scotland match those in
Newfoundland (Canada)
• Changes in earths magnetic field
Why do plates move?
Sea floor spreading or Ridge Push is
where lava rises vertically through the
crust and forces the outward movement
of the plates. This can be a hotspot, or
form a mid ocean ridge at divergent
plate boundaries.
The movement of these huge plates is driven by convection
currents in the Earth’s mantle. The core heats up the mantle and
this begins the cycle of magma rising to the crust, cooling and
sinking back down, pulling the plates with it.
Slab pull is also a driver,
where the subduction of
the oceanic plate drags
the rest of the plate with
it. It subducts due to
being more dense.
Divergent (Constructive) Boundary
Plates move apart, allowing magma to rise and form new crust. Example: Mid-Atlantic Ridge.
Convergent (Destructive) Boundary
Plates collide, and one plate is forced beneath the other (subduction), leading to earthquakes and volcanic activity. Example: Pacific Ring of Fire.
Transform (Conservative) Boundary
Plates slide past each other horizontally, causing friction and earthquakes but no new crust formation. Example: San Andreas Fault, California, USA.
Collision Boundary
A type of convergent boundary where two continental plates collide, creating mountains instead of subduction. Example: Himalayas (India-Eurasia collision).
Paleomagnetism
Involves studying the
rocks formed by underwater volcanic
eruptions in relation to the Earth’s
magnetic field.
Benioff Zone
The Benioff Zone (also known as the Wadati-Benioff
Zone) is an area of seismicity corresponding with the
slab being thrust downwards in a subduction zone,
usually at a 45-degree angle.
The different speeds and movements of rock at this
point produce numerous earthquakes.
The Benioff Zone is the site of intermediate/deep-
focused earthquakes.
This theoretical framework is an important factor in
determining earthquake magnitude as it determines
the depth and position of the hypocentre.
Extends from the surface to depths of 650-700km
Theory of continental drift
he continental landmasses were “drifting” across the Earth, sometimes plowing through oceans and into each other.
Evidence of Plate tectonics
• Fit together like jigsaw pieces
• Fossil remains on one continent
and another
• Evolution of animals, who once
lived together.
• Rock type similarities- the
geological sequence of
sedimentary and igneous rocks in
parts of Scotland match those in
Newfoundland (Canada)
• Changes in earths magnetic field
Why do plates move?
Sea floor spreading or Ridge Push is
where lava rises vertically through the
crust and forces the outward movement
of the plates. This can be a hotspot, or
form a mid ocean ridge at divergent
plate boundaries.
The movement of these huge plates is driven by convection
currents in the Earth’s mantle. The core heats up the mantle and
this begins the cycle of magma rising to the crust, cooling and
sinking back down, pulling the plates with it.
What happens where the plates me
Slab pull is also a driver,
where the subduction of
the oceanic plate drags
the rest of the plate with
it. It subducts due to
being more dense.
The
Divergent (Constructive) Boundary
Plates move apart, allowing magma to rise and form new crust. Example: Mid-Atlantic Ridge.
Convergent (Destructive) Boundary
Plates collide, and one plate is forced beneath the other (subduction), leading to earthquakes and volcanic activity. Example: Pacific Ring of Fire.
Transform (Conservative) Boundary
Plates slide past each other horizontally, causing friction and earthquakes but no new crust formation. Example: San Andreas Fault, California, USA.
Collision Boundary
A type of convergent boundary where two continental plates collide, creating mountains instead of subduction. Example: Himalayas (India-Eurasia collision).
Paleomagnetism
- Involves studying the
rocks formed by underwater volcanic
eruptions in relation to the Earth’s
magnetic field.
Benioff Zone
The Benioff Zone (also known as the Wadati-Benioff
Zone) is an area of seismicity corresponding with the
slab being thrust downwards in a subduction zone,
usually at a 45-degree angle.
The different speeds and movements of rock at this
point produce numerous earthquakes.
The Benioff Zone is the site of intermediate/deep-
focused earthquakes.
This theoretical framework is an important factor in
determining earthquake magnitude as it determines
the depth and position of the hypocentre.
Extends from the surface to depths of 650-700km.
Landform formation
Ocean Trench
• Process: Formed at convergent (destructive) plate boundaries, where one tectonic plate is subducted beneath another.
• Formation: As the denser oceanic plate sinks into the mantle, it creates a deep trench in the ocean floor.
• Example: Mariana Trench (Pacific Plate subducting under the Mariana Plate).
Fold Mountains
• Process: Formed at collision boundaries when two continental plates push against each other.
• Formation: The crust is compressed, causing it to buckle and fold upwards over millions of years.
• Example: Himalayas (Indian and Eurasian Plates colliding).
Ocean Ridges
• Process: Formed at divergent (constructive) boundaries, where two oceanic plates move apart.
• Formation: Magma rises from the mantle, cools, and forms new oceanic crust, creating a continuous mountain chain on the ocean floor.
• Example: Mid-Atlantic Ridge (Eurasian and North American Plates moving apart).
Volcanic Island Arcs
• Process: Formed at oceanic-oceanic convergent boundaries, where one oceanic plate subducts under another.
• Formation: The subducted plate melts, creating magma that rises to form volcanic islands in an arc shape.
• Example: Japan (Pacific Plate subducting under the Eurasian Plate).
Hotspot Volcanoes
• Process: Formed by mantle plumes, where a column of hot magma rises through the lithosphere.
• Formation: Magma breaks through the crust, forming a volcanic island. As the plate moves, new volcanoes form, creating a chain.
• Example: Hawaiian Islands (Pacific Plate moving over a stationary hotspot).
