Unit 4- Earth's Layers Flashcards
the outer most later is called
Crust
how many compositional (chemical) layers does Earth have?
3
Name 2 types of crust
Oceanic
Continental
Oceanic and Continental crust is mostly made from what?
Oxygen, Silicon, and Aluminum
the middle layer is called what
Mantle
The innermost layer of the earth is what?
core
The innermost layer is mostly made of what?
Iron and Nickel
The innermost layer makes up about how much of Earth’s mass?
1/3
how many physical layers of the earth have?
5
what properties do scientists use to develop these layers?
whether it’s a solid or liquid
how the layer move forward transmits waves
describe the properties of the lithosphere
- The outermost rigid layer
- made up of two parts the crust and the ridge
- The lithosphere is divided into pieces call tectonic plates
describe the properties of the asthenosphere
- A weak or soft mantle that is made of rock that flows slowly
- tectonic plates move on top of this layer
describe the properties of Mesosphere
- The strong lower part of the mantle
- Rock flows more slowly than rock in the asthenosphere does
describe the properties of the outer core
- The liquid layer of Earth’s core
- it lies beneath the mantle and surrounds the inner core
describe the properties of the inner core
A solid dense center of our planet
Who first proposed the hypothesis of continental drift and when?
Alfred Wegener
late 1800
what is continental drift
- A hypothesis proposed by Alfred Wegener
- he proposed that the continents once formed a single landmass, broke up, and drifted
explain Wegener’s evidence to support his hypothesis
- fossils of the same species found on continents on different sides of the Atlantic Ocean
- locations of the mountain ranges
- Rock formations
- evidence of the same ancient climatic conditions on several continents
what is Pangaea
scientists think that about 245 million years ago the continents were joined in a single large landmass (called Pangaea)
explain what happened 245 million years ago
- continents were joined in a single large landmass called Pangaea
- as the continents collided to form Pangaea, mountains formed
explain what happened 200 million years ago
A large wrist forms and Pangaea begin to break into two continents Laurasia and Gondwana
- The rift eventually formed the north Atlantic Ocean
- The continents broke into other continents
explain what happened at 150 million years ago
A rift between Africa and South America open to form the South Atlantic Ocean
explain what happened and 50 million years ago
India collided with Eurasia and the Himalaya Mountains began to form
why was Wegener’s idea of continental drift pushed aside?
-scientists could not determine how continents moved
-
what happened in the 1950s for scientist to look at Wegener’s hypothesis again
scientists found huge underwater mountain ranges called mid-ocean ridges
what were the three pieces of evidence to support Wegener’s hypothesis?
- age and magnetic properties of the seafloor
- seafloor spreading
- Ocean trenches
explain age and magnetic properties of the seafloor
mid ocean ridges form along cracks in the crust
Rock samples from the sea floor revealed that the youngest rock is closest to the ridge, while the oldest rock is furthest away
describe the seafloor spreading
it explains the age and magnetic patterns of seafloor rocks, scientists propose a process called seafloor spreading
-in this process, molten rock from inside Earth rises through the cracks in the ridges, cools, and forms new oceanic crust
explain ocean trenches
- Earth is not getting larger although the seafloor has been spreading, because they found huge trenches, like deep canyons, in the seafloor
- at these sites oceanic crust is sinking to the asthenosphere
- older crust is being destroyed at the same rate new crust is forming. Thus, earth remains the same size.
describe plate tectonics
- A large scale movements of earth’s lithosphere which is made up of the crust and the ridge, upper part of the mantle
- Plate tectonics explains how and why features in the Earth’s crust form and continents move
describe tectonic plates
The lithosphere is divided into pieces called tectonic plates
which is more dense continental or oceanic plates?
oceanic
how many plate boundaries are there?
3
describe a convergent plate boundary
- A convergent boundary forms when two plates collide
- when two tectonic plates of oceanic lithosphere collide, one of the plate subducts, or sinks, under the other plate,
what is an example of a convergent boundary
continent to continent collision
Continental ocean collision
Ocean the ocean collision
describe a divergent plate boundary
- it is when two plates move away from each other
- most divergent boundaries are located on the ocean floor
described a transform boundary
- boundary at which two plates move past each other horizontally
- they scrape against each other in a series of sudden slippages of crustal rock that are felt as earthquakes
- they generally do not produce magma, unlike other types of boundaries
what causes tectonic plates to move?
mental convection
ridge push
slab pull
describe Mantle convection
- some parts of the mantle become hotter than other parts. The hot parts rise as the sinking of cooler, denser material pushes the heated material up.
- this kind of movement of material due to differences in density
describe ridge push
- newly formed the rock at mid ocean ridge is warm and less dense than older, adjacent rock.
- this force, called ridge push, pushes the rest of the plate away from the mid ocean ridge
describe slab pull
- At subduction zones, a denser tectonic plate sinks, or subducts, beneath another, less dense plate.
- as it sinks, the leading edge of the plate pulls the rest of the plate with it.
- this evidence leads many scientist to think that slab pull may be the most important mechanism driving tectonic plate motion
describes the mantle
- located between the core and the crust
- it is a region of hot, slow flowing, solid rock
convection
the movement of matter that results from differences in density caused by many variations in temperature
how does convection work in this layer?
cooler rock sinks and warmer rock rises
