GEOG 1 - Quiz 4

How old is the Earth? Did it always have life and water?

4.6B years old

It did not begin with life and water

How did life in oceans begin in the First era of complex life?

Single microbes and bacteria, which then turned into aquatic multicellular organisms

What % of aquatic animals went extinct due to The Great Dying?

96%

In the second era of complex life, what hapened to reptiles?

dinosaurs went extinct due to an asteroid that hit Earth

Now we have remnants of them through birds, crocodiles, cockroaches which have evolved over time.

What is the third era of complex life?

Age of mammals which is current

What are the 3 basic components of Earth’s structure?

Crust (40-60mi)

Mantle (1800mi)

Core (2100mi)

What component of the Earth is most dense? Why?

The core because it is 1/3 of the Earth’s mass

What component of Earth’s structure is the hard layer? Why?

Crust because it sits on top of the asthenosophere

How did we get water?

Comets!

• They hold ice that eventually melts down into water

Are geographic north and magnetic north the same?

No. They are in different areas bc magnetic earth is shifting toward Russia.

What causes the magnetic north to shift toward Russia?

• migration of animals

• solar flares

• radiation

Certain spots got more heat.

How do igneous rocks form?

When magma within the Earth’s surface or lava cool down.

• Fiery

How are intrusive igneous rocks formed? Give ex rocks

form slowly from magma under the Earth’s surface

• granite

How are extrusive igneous rocks formed? Give ex rocks

form quickly from lava at the surface when volcanoes erupt

• obsidian and pumice

How are sedimentary rocks formed?

From weathering and erosion.

• soft: sediments accumulate over time (sand particles, mud, organic material from lakes or oceans)

How are metamorphic rocks formed? Give ex rock

altered by extreme heat and/or pressure (any rock can turn metamorphic pressure)

• Marble

We are currently in the ___ era of complex life on Earth.

Third

___ rocks are formed by extreme heat and/or pressure.

Metamorphic

___ rock form quickly from volcanic lava flows.

Extrusive igneous

The shifting of the magnetic poles will result in ____.

the change of animal migration and solar flares would be more intense.

What happens with tectonic plates?

Always moving.

Land splits up due to plates moving and seafloor spreading.

The Earth’s formation will look different in millions of years.

What is a divergent boundary?

When plates are moving apart.

Magma flows upwards and pushes adjacent plates apart.

New crust is created and drives continental movement.

Plates would not move without it.

What is a convergent boundary?

Plates colliding.

Oceanic plates slide down and continental plates push up.

How does subduction occur? What does it create?

When an ocean plate meets a continental plate

• Oceanic: slides down

• Continental: pushes up

Creates trenches and mountains.

How does collision occur?

When two continental plates collide and are the same density

What way do continental plates push and why?

They both push upward because neither are yielding

What happens to crust from a collision?

It is displaced and turned into mountains.

How much does Mt. Everest grow every year?

1/3 to ½ taller every year

What happened to India 40 million years ago?

It was an island pushed northward into Asia.

How do we know India was an island?

There were unique dinosaurs.

What is a transform boundary? What is true about the motion?

When two plates slide past each other

Motion: horizontal

What kind of boundary is taking place in California?

80% a transform boundary

→ Rarely earthquakes above 8.0

Why are there transform boundaries?

Very gradually, movement happens deep in the Earth’s crust

What determines earthquake faults?

Plate boundary type

Where are the top 10 strongest earthquakes in?

Convergent zones, specifically subduction zones.

Are the deadliest earthquakes always in subduction zones?

not always

What other factors than magnitude influence death tolls from earthquakes?

Infrastructure

Location

Depth

Duration

Time of day

Tsunami

LIDDTT (abbreviation to help)

What do we use to measure earthquakes from the 1930s-1970s? Describe it!

Richter Scale

• logarithmic

  • each point is 10x stronger

    • EX: 7.0 is 100x stronger than 5.0

What are the limitations of the Richter scale?

Only measures energy

• Doesn’t account for depth

Machine maxes out at 8.0

What do we use to measure earthquakes from 1970s-now? Describe it!

Moment magnitude scale

• fully electric seismometer

• still logarithmic

• digitally calculated

• takes into account depth and distance of fault movement

What plate are LA and SD moving toward?

pacific plate

What is true about the San Andreas fault?

Drifts 2 inches every year

1,000,000 years LA will separate from Cali

Which plate boundary type is where old crust is destroyed back into magma?

convergent

Which plate boundary type is where the force for continental movement originates?

___ zones of convergent boundaries are responsible for most tsunami formation.

subduction

What factor is least likely to play a role in an Earthquake’s toll?

• Duration of shaking

• Depth of quake

• Infrastructure

• Time of day

• Weather

Weather

What part of the atmosphere are volcanoes?

asthenosphere

How many eruptions take place on Earth at any time of day?

20-30

How are volcanoes considered active?

has erupted in the last 10,000 years

How are volcanoes considered dormant?

active, not currently eruption, could erupt

• we still don’t know factors that make volcanoes dormant

How are volcanoes considered extinct?

has not erupted in the last 10,000 years

What % of volcanoes are in the Ring of Fire?

75%

What % of volcanoes are underwater?

70%

This is why we don’t really hear about them

What happens to lava underwater?

it solidifies

Magma from divergent boundaries

1. where does it come from?

2. describe viscosity/texture

3. describe eruptions

1. magma directly from asthenosphere

2. normal viscosity and texture

3. smooth, constant eruptions. no blockage.

Magma from convergent boundaries

1. where does it come from?

2. describe viscosity/texture

3. describe eruptions

1. oceanic crust melted

2. high viscosity. thick, clumpy. rock and magma mixed together like cottage cheese and oil.

3. explosive, something is blocked so build-up created

Describe the shape of cinder-cone volcanoes.

small, symmetrical and cone-shaped

bowl-shaped crater at the summit

How do cinder-cone volcanoes form?

Fast-growing with a single vent

• 100ft/week or 10000ft/year

How high in elevation can cinder-cone volcanoes go?

10000ft

Describe the eruption of cinder-cone volcanoes.

Usually erupts once or twice a year

Mostly ash yet explosive

Describe the shape and size of shield volcanoes

Biggest volcanoes on earth

Hugh gently sloped (“shield like”)

Wide base several miles in diameter

How are shield volcanoes formed?

from thin lava slowly spreading from a central vent

Describe the eruptions of shield volcanoes

Frequent but gentle

• like liquid overflowing from a container

More lava, less ash.

Not very dangerous because rarely explosive.

What are hotspots? What do they cause?

Uniquely spots within plates that allow magma to escape.

Hot spots grow islands

• hawaiian chain due to hotspot

Describe the shape of composite volcanoes.

Tall, steep-sided, can be symmetrical

How are composite volcanoes formed?

from layers of thick lava and ash.

How high in elevation can composite volcanoes go?

up to 8,000 ft

Describe the eruptions of composite volcanoes.

Rare but deadly

May blow out the sides

What are the two types of eruptions?

Effusive and Explosive

What are effusive eruptions? Which types of volcanoes do they come from?

gentle, thin lava, low viscosity, gases escape easily

shield and most underwater volcanoes

What are explosive eruptions? Which types of volcanoes do they come from?

violent, thick lava, high viscosity, compressed gases are trapped

cider cone and composite volcanoes

what is a caldera?

large basin-shaped depression formed out of collapsed volcanoes

What causes the most deaths from volcanic eruptions?

Hot gas

What types of lava are there?

A’a: slower, thicker, cooler

Pahoehoe: faster, thinner, hotter

both slow and theoretically walkable

Describe pyroclastic flows.

60mph

500-1800F

Death on contact

What is one of the strongest eruptions in modern history?

Eruption of Krakatoa 1883

What were the immediate effects of Krakatoa?

pyroclastic flows traveled 25mi away

triggered 130ft tsunamis

3600 died but if it were today millions would have died

sound of eruption was loudest sound recorded 310decibels

What were the long-term effects of Krakatoa?

ash blocked the sun

volcanic winter conditions

global avg temp dropped 2.2F

four years of unusually cold weather

vividly red sunsets

In what years did weather conditions return to normal from Krakatoa?

1888

___ boundary volcanoes have lower viscosity magma, resulting in effusive eruptions.

divergent

Which volcano type is the largest, with a base measuring several miles in diameter?

shield

Which volcano type is the fastest-growing and most common?

cinder cone

Which volcano is credited with the formation of the Hawaiian island chain?

shield

Which volcano type produces the most wide-scale and deadliest eruptions?

composite/stratovolcano