Ch. 12 - The Dynamic Planet

Question 1

Who was the first person to look at the age of the earth?

Answer 1

Archbishop James Ussher in the 1650’s

Question 2

Who was James Hutton and what did he propose?

Answer 2

He proposed the Principle of Uniformitarianism in the 1790s.

Question 3

What is the Principle of Uniformitarianism?

Answer 3

This principle claimed that basic geologic processes don’t change over time, they always stay the same

“The present is the key to the past”

Question 4

What are the two methods of dating geologic formations?

Answer 4

Relative Dating

Absolute Dating

Question 5

What is the Principle of Original Horizontality?

Answer 5

States that layers of sediment are originally deposited horizontally under the action of gravity. Sediments, at the bottom of a lake for example, will be oriented horizontally, as long as it’s not disturbed

Question 6

What is the Principle of Superposition?

Answer 6

In any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom

Question 7

What is the Principle of Cross-Cutting Relationships?

Answer 7

States that the geologic feature which cuts another is the younger of the two features

Question 8

What is the difference between Relative Dating and Absolute Dating?

Answer 8

Relative Dating: Puts geologic events into more of a sequence of events.

Absolute Dating: Provides actual dates or date ranges, in numbers of years, for rocks.

Question 9

What is an Isotope?

Answer 9

Groups of a certain element (Carbon, Hydrogen, Oxygen, etc) that have different Atomic Masses (12C, 13C, 14C)

Question 10

How can the Absolute Date of an element/specimen be determined?

Answer 10

Radioactive decay is the key.

By calculating the atomic mass, and then referring to the half-life of that specific isotope, the absolute age of the chemical element can be determined

Question 11

What is the sequence of layers of earth, starting from Core?

Answer 11

Core—-Moho Discontinuity—Mantle—Guttensberg Discontinuity—Core

Question 12

How is the earth’s core composed?

Answer 12

There is the Inner and Outer layers of the core

Inner core is solid, and has the highest density

Outer core is molten (composed of iron)

Question 13

How is the earth’s Mantle composed?

What are the layers ?

Answer 13

Lower Mantle - Upper Mantle - Asthenosphere - Uppermost Mantle

Mantle makes up 80% of the earth’s volume, and is made up of solid minerals

Question 14

How is the Asthenosphere composed?

Answer 14

Asthenosphere is not solid, behaves like plastic. All the material above the asthenosphere has immense weight, so the asthenosphere materials below begin to deform.

A driving force in the process of plate tectonics

Question 15

What are the two types of earth’s crust?

Answer 15

Oceanic + Continental

Question 16

What are the characteristics of Oceanic Crust?

Answer 16

Density of 3.0g/cubic centimetre

Mainly composed of Magnesium and Silica (Magnesium is what makes it dark in color)

5km thick on average

Question 17

What are the characteristics of Continental Crust?

Answer 17

Density of 2.7g/cubic centimetre

Mainly composed of Silica and Aluminium minerals

Thickness between 30-60km

Question 18

What is the definition of a “Mineral”?

Answer 18

A natural, inorganic solid substance with fixed proportion of elements and definitive crystalline structure. (ex: NaCl, SiO2)

1. Has to be natural
2. Inorganic
3. Solid (Ice is a mineral, water is not)
4. Fixed proportion of elements
5. Definitive crystalline structure

Question 19

Which elements make up most of the earth crust’s weight?

Answer 19

Oxygen (46%)

Silicon (27%)

Aluminium (8%)

Question 20

What are the six mineral identification methods?

Answer 20

• Luster (how well it reflects light)
• Colour and streak (color it leaves when you scratch it on a tile)
• Hardness
• Cleavage and fracture
• Heft / Specific Gravity (weight and buoyancy)
• Reaction with acid

Question 21

What is the definition of a “Rock”?

Answer 21

Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids

Question 22

How are Igneous Rocks formed?

Answer 22

From the cooling and solidification of magma or lava

Question 23

What is Extrusive Igneous Rock?

Answer 23

Magma that cools above the surface of the earth; BASALT, PUMICE, OBSIDIAN

Question 24

What is Intrusive Igneous Rock?

Answer 24

Intrusive igneous: Magma that cools below the earth’s surface; GRANITE; GRANODIORITE

Question 25

What is the general composition of Igenous Rock?

Answer 25

Felsic (composed of Iron and Silicon)

Mafic (Magnesium; dark in color)

Question 26

What are the two primary sources of Sedimentary Rocks?

Answer 26

1. Clastic (composed of fragments of other rocks)
   Ex: CONGLOMERATE, SANDSTONE, SHALE
2. Chemical (made through chemical processes)
   Ex: LIMESTONE, COAL

Question 27

What is the order of clastic sedimentary rocks in terms of clast size; biggest to smallest?

Answer 27

Breccia/Conglomerate, Sandstone, Siltstone (mudstone), Shale

Question 28

How are Metamorphic Rocks formed?

Answer 28

The original rock is subjected to heat and pressure, causing profound physical or chemical change

Question 29

What does foliated and non-foliated mean?

Answer 29

Foliation forms when pressure squeezes the flat or elongate minerals within a rock so they become aligned. These rocks develop a platy or sheet-like structure that reflects the direction that pressure was applied in

Question 30

What are common Non-foliated rocks?

Answer 30

Marble comes from Limestone

Quartzite comes from Sandstone

Question 31

What are common Foliated rocks?

Answer 31

Schist comes from Shale

Gneiss comes from Granite

Question 32

Who originally proposed, but couldn’t prove, the theory of Plate Tectonics / Continental Drift?

Answer 32

Alfred Wegener in the early 20th Century

Question 33

How many tectonic plates are on the earth’s lithosphere?

Answer 33

14

Question 34

How fast do tectonic plates move on average?

Answer 34

A few centimetres per year

Question 35

What are the characteristics of Divergent plate boundaries?

Answer 35

Oceanic: Rising of magma pushes the oceanic crust up slightly higher, not perfectly horizontal. A ridge is created.

Continental: Separation of continental crust forms a break in the layer, giving things like a magma a chance to rise through the crust, and potentially reach the earth’s surface

Volcanoes can be formed in this process, as well as rift valleys when continental crust separates faster than magma rises

Mid-Atlantic Ridge

Question 36

What can happen if two Oceanic plates converge?

Answer 36

Subduction can occur, if one plate is denser than the other

Trenches can be formed, like Mariana’s trench

Volcanic Island Arcs can form/ Volcanoes

Earthquake can happen

Question 37

What can happen as a result of Oceanic and Continental plates converging?

Answer 37

• When one slab of oceanic crust and a slab of continental crust converge
• The oceanic crust is denser, so it sinks beneath the continental.
• Moving deeper and deeper into the earth, the oceanic crust heats up, magma forms, and rises to the earth’s surface creating volcanoes and mountains.
• Earthquakes can also happen in these boundaries, as well as trenches
• This example describes Vancouver’s geographic location and physical surroundings.

Question 38

What can happen from two Continental plates converging?

Answer 38

• It’s easier for crust to move upwards when the densities are the same, as opposed to them both sinking.
• There is still a lot of friction, which can result in earthquakes
• Volcanoes are unlikely to form in this process, because there is no magma being formed or heating up. Non-volcanic mountains are the usual formation

Question 39

What is the general outcomes of Transform boundaries?

Answer 39

Earthquakes, occasionally very intense ones

Question 40

How do you know if it’s a Right Lateral or Left Lateral transform boundary?

Answer 40

The direction each plate moves in respect to the other, if you were standing facing the boundary.