1.1 C: Geology = the Changing Earth 1.1 The Long Beginning Flashcards
What is the Slave Granite?
A red belt of granite rock that is among Alberta’s oldest rocks, approximately two billion years old.
The Slave Granite is part of the Precambrian Shield.
What is the Precambrian Shield often called?
The Canadian Shield.
It is a significant geological feature of Canada.
How old is the Precambrian Shield?
It is part of the original North American continent that formed four billion years ago.
The Precambrian Shield was formed in the Precambrian Era.
What percentage of Canada’s land mass does the Precambrian Shield cover?
More than half.
It includes most of Ontario and Quebec.
How deep would you typically have to dig in Alberta to reach the basement rock?
Several thousand metres below the surface. (That’s several kilometres)
What is an outcrop?
A rock layer that is normally underground but is exposed above the surface.
Examples include mountain rock faces, canyon walls, river valley cliffs, and coastal cliffs.
What are some examples of outcrops?
Examples include:
* Mountain rock faces
* Canyon walls
* River valley cliffs
* Coastal cliffs
What is the Precambrian Era?
The first major section of geological time, lasting from the origin of Earth 4.5 billion years ago up to 590 million years ago.
Earth is 4.543 billion years old!
True or False: The Precambrian Shield is part of the original North American continent.
True.
What can be observed in a sample of granite?
Large mineral crystals of various shapes, sizes, and colours
These minerals are formed under extreme conditions.
What temperatures are required for certain minerals in granite to form?
900°C to 1000°C
These temperatures indicate extreme geological conditions.
How old is the Slave Granite rock mentioned in the text?
Two billion years old
What must be considered to understand the formation of granite?
The composition of Earth’s interior
What is the approximate depth of the deepest mines and wells compared to Earth’s radius?
Deepest mines (about 3 km) and wells (about 13 km) barely scratch the surface
Earth’s radius is over 6000 km.
How is Earth’s internal structure described?
Separated into layers arranged according to densities
What happens to the densest materials in Earth’s interior?
They sink to the center
Fill in the blank: The Earth’s interior cannot be observed directly because the deepest mines and wells barely scratch the _______.
surface
True or False: The Earth’s internal structure is uniform throughout.
False
What is the main factor that causes the arrangement of Earth’s internal layers?
Density
What is the innermost layer of Earth called?
Core
The core is divided into a solid inner core and a liquid outer core.
What materials primarily make up Earth’s core?
Nickel and iron
These materials contribute to the high density of the core.
How can the structure of Earth be analogized to a hard-boiled egg?
The core is like the yolk
This analogy illustrates the core’s position as the densest layer of Earth.
What are the two parts of Earth’s core?
Solid inner core and liquid outer core
The inner core is solid, while the outer core is liquid.
What induces Earth’s magnetic field?
Liquid outer core
The movement of the liquid outer core generates the magnetic field.
What is the approximate radius of Earth?
6400 km
This measurement is a standard approximation of Earth’s radius.
What is the thickness of the lithosphere?
125 km
The lithosphere is the rigid outer layer of Earth.
Fill in the blank: The densest material sinks to the _______ while the least dense material floats on the surface.
centre
This principle explains the layering of Earth’s materials based on density.
True or False: The core of the Earth consists only of a solid inner part.
False
The core has both a solid inner core and a liquid outer core.
What is the mantle?
A solid layer comprising about 80% of Earth’s volume
It is predominantly solid but, on geologic time scales, it behaves as a viscous fluid, sometimes described as having the consistency of caramel. Partial melting of the mantle at mid-ocean ridges produces oceanic crust, and partial melting of the mantle at subduction zones produces continental crust.
What causes zones of rock within the mantle to behave plastically?
Extreme heat and pressure
How does the flow of toothpaste relate to the mantle’s behavior?
It is analogous to the flow of a plastic material
What floats on the upper part of the mantle?
Earth’s crust
What is the upper part of the mantle called?
Asthenosphere
What characterizes the asthenosphere?
It is the least rigid and most plastic part of the mantle
Fill in the blank: The plastic nature of the asthenosphere can be witnessed when _______ from the asthenosphere rises up in the form of volcanoes.
magma
What is the mesosphere in geology?
The part of the mantle beneath the asthenosphere
The mesosphere is more rigid compared to the asthenosphere.
What is the lithosphere?
Earth’s outermost rigid layer of rock
The lithosphere is often compared to the shell of an egg.
What is the difference between the mesosphere and the part of the atmosphere that has the same name?
The mesosphere in geology refers to a layer in the Earth’s mantle, while the atmospheric mesosphere is a layer in the atmosphere
It is important not to confuse these two distinct geological and atmospheric layers.
Fill in the blank: The lithosphere is like the _______.
shell of the egg
What characterizes the part of the mantle beneath the asthenosphere?
It is more rigid and called the mesosphere
This rigidity differentiates the mesosphere from the more ductile asthenosphere above it.
What is the primary method scientists use to study the layers below the lithosphere?
Indirect evidence from events like earthquakes.
What is one theory regarding the heat energy needed to drive the plastic flow of material in the mantle?
Nuclear decay deep within the core provides much of the heat energy.
What analogy is used to describe the movement of matter in the mantle?
A hot bowl of French onion soup.
What is the process called that describes the movement of material in the mantle?
Convection.
Fill in the blank: The movement of hotter material in the mantle rises towards the crust, then cools and _______.
sinks.
True or False: Scientists can directly observe the layers below the lithosphere.
False.
How does convection affect the crust of the mantle?
It causes the crust to crack, tear, and move.
What drives the plastic flow of material in the mantle?
Heat energy from nuclear decay.
What is the significance of earthquakes in studying Earth’s structure?
They provide indirect evidence for theories about the layers below the lithosphere.
What is the process at work in Earth’s mantle that affects the solid crust?
Enormous convection cells
These convection cells push and pull on Earth’s solid crust.
How does the convection process change the idea of Earth’s structure?
Requires a revision to the idea that Earth is like an egg
The lithosphere is compared to the shell of an egg but is not a single rigid cover.
What are crustal plates?
Large pieces of continental crust or oceanic crust that float and slowly move atop the asthenosphere
These plates are part of the lithosphere.
True or False: The lithosphere is a single rigid layer.
False
The lithosphere is described as a mosaic of rigid pieces.
Fill in the blank: The lithosphere is more like the cracked shell of an egg, consisting of a mosaic of _______.
rigid pieces
These pieces are referred to as crustal plates.
What do the crustal plates float on?
The asthenosphere
The asthenosphere is the layer beneath the lithosphere.
What is the movement speed of lithospheric plates per year?
Slowly moves
The exact speed can vary but is generally in centimeters per year.
What is paleomagnetism?
The study of the magnetic properties of ancient rocks to provide evidence for plate tectonics.
Paleomagnetism helps understand the historical movement of tectonic plates.
What process is referred to when crustal plates separate at mid-oceanic ridges?
Sea-floor spreading.
This process indicates that the youngest rocks are found closest to the ocean ridges.
What happens to the age of rocks as they move away from ocean ridges?
The rocks steadily get older.
This has been verified by deep-sea drilling operations.
What drives the movement of crustal plates?
Convection currents of hot material from within the mantle.
This is a fundamental principle of plate tectonics.
True or False: The youngest rocks on oceanic plates are located farthest from the spreading center.
False.
The youngest rocks are closest to the spreading center.
Fill in the blank: The explanation for the movement of the Earth’s crustal plates is called _______.
plate tectonics.
Plate tectonics is a theory that describes the large-scale movements of Earth’s lithosphere.
What is the significance of core samples taken from the ocean floor?
They show a steady increase in age away from the ocean ridges.
Core samples provide physical evidence supporting the theory of sea-floor spreading.
What do sections of the sea floor with rocks having magnetic fields pointing in the opposite direction indicate?
The magnetic field of Earth has reversed more than once in the past several million years.
This phenomenon is crucial for understanding Earth’s geological history.
What happens at the end of an oceanic crustal plate that is opposite the fracture when two oceanic plates are moving apart?
The edge of the oceanic crustal plate is pushed under the neighboring continental crustal plate.
This process is part of subduction, where one plate moves beneath another.
What occurs to the oceanic crustal plate as it is forced down into the mantle?
The oceanic crustal plate melts.
This melting contributes to volcanic activity and the formation of new crust.
What is the significance of the alternating normal and reversed magnetic stripes found on the ocean floor?
They are parallel to the oceanic ridges and provide evidence for sea-floor spreading and plate tectonics.
This pattern reflects the history of Earth’s magnetic field changes.
How does the pattern of magnetic alignments on one side of an ocean ridge compare to the other side?
It is the mirror image of the pattern on the other side.
This symmetry supports the theory of plate tectonics.
What does paleomagnetism provide evidence for?
Sea-floor spreading and plate tectonics.
Paleomagnetism studies the magnetic properties of rocks to understand historical geological processes.
How was the Slave Granite formed?
At the collision site of two continental crustal plates about two billion years ago.
This formation process is significant because both plates had equal densities.
Why couldn’t one continental plate slide under another during the formation of the Slave Granite?
Both plates had equal densities.
This resulted in the plates welding together instead of subducting.
What happened over a long period of time to the mountain ranges that were formed during the collision of the continental plates?
They have long since eroded.
The erosion process is a natural outcome of geological activity over time.
How old are Alberta’s oldest rocks compared to the age of Earth?
Alberta’s oldest rocks are two billion years old, which is about half the age of Earth.
Earth is approximately 4.5 billion years old.
What layers did Earth settle into after surviving violent interplanetary collisions?
The core, the mantle, and the crust, depending on their density.
This stratification is crucial for understanding Earth’s structure.
What continues to heat the core and mantle of the Earth?
Nuclear reactions.
These reactions lead to enormous convection currents within the Earth’s interior.
True or False: The Slave Granite is considered one of the oldest rocks in Alberta.
True.
It provides insight into the geological history of the region.
