Earth part two Flashcards
what is the name for the amount of light being recieved by the sun
insolation
When the amount of radiation coming to the earth from the sun increases, what is this called
solar forcing
Which changes temperature quicker
land or water?
why?
land
It has a lower volumetric heat capacity
What are the five cyclical factors, relating to the earth’s movement that effect the amount of energy coming from the sun / and or its distribution on earth
Orbital shape (eccentricity)
Axial tilt variation
Axial precession
Apsidal precession
Orbital inclination
What is the cyclical timescale for variantion to the earth’s orbital eccentricity
what happens?
what causes this change?
There are several cycles, but they combine together to form an approximately 100,000 yr cycle
what the earth’s orbit goes from being nearly circular to more elliptical and back.
The gravitational pull of Jupiter and Saturn are the main factors in creating these variations
What is the correct astronomical term for axial tilit
Between what angles does earth’s axial tilt vary
Over what cyclical length
What is currently doing, decreasing or increasing?
When was it last at maximum
What would the current trend normally mean (all else being equal for climate)
Obliquity
It is the angle between an object’s rotational axis and its orbital axis, or, equivalently, the angle between its equatorial plane and orbital plane
22.1 and 24.5
41,000 year cycle
It is currently decreasing
Last at maximum in 8,700 BCE
So decreasing tilt means less seasonal variation - colder at the poles!
What is the technical name for Earth’s orbital plane
ecliptic plane
Can you visualise axial precession
What is the cyclical duration for this
What causes it?
What hemisphere is currently in summer during perihelion
25,772 years (call it 26,000)
It is caused by the tidal forces of the Sun and Moon - both contribute roughly equally
Currently, perihelion occurs during the southern hemisphere’s summer.
This means that whether in the southern hemisphere is more extreme
You’ve known for ever that the axial tilt goes through precession
What else does? and what’s it called?
How long does a full cycle take
The orbital elipse also precesses
Its called Apsidal precession
A full cycle takes 112,000 years relative to the fixed stars
What is the earth’s current orbital inclination
Over what cyclical timescale does it move up and down
1.57 degrees
about 70,000 years
(however, when measured relative to the plane representation the angular momentum of the Solar System - approx. the orbital plane of Jupiter) it is 100,000 years
What was the predominant climate cycle from 1-3 million years ago
What has been over the last 1m years
What earth cycles do these match
It was 41,000 (oliquity)
now its 100,000 (eccentricity)
When was the last ice age period
what was it called
What things might have caused it?
What was the most substantial period before hand
When were glaciers at the most extensive and how low were sea levels
Younger Dryas - 12,900 - 11,700 before present.
It was an interuption to the warming period of the LGM below
A popluar idea is that is was caused by a failure of thermohaline circulation
However some pretty substantial research published in 2018 suggest it was an impactor - basically debris from a large comet. The research conducted all over the world suggests that 90% of the earth’s landsurface was set on fire!
Last Glacial Maximum (LGM) - 27,000 - 13,000 before present
21,000 before present - 125m below present
At least how long has earth’s magnetic field existed
3.45 billion years
When is the name of the CME that occured in 1859
The Carrington Event
This massive CME released … the equivalent to 10 billion Hiroshima bombs exploding at the same time. [It] hurled around a trillion kilograms [a million tons] of charged particles towards the Earth at speeds of up to 3,000 km/s [1900 miles/sec]. Its impact on the human population, though, was relatively benign as our electronic infrastructure at the time amounted to no more than about 200,000 kilometers [120,000 miles] of telegraph lines.
When was the last really big solar storm
what physical consequence did it have?
March 1989 storm
It sparked a collapse of the Hydro-Quebec power grid causing a nine-hour electrical blackout
How long ago was the last complete geomagnetic reversal on earth
How much has the earth’s magnetic field reduced since 1840
What is the particularly concerning artifact
What happened between 105-92k years ago?
Why would this be bad now?
780,000 years ago (it happens about twice per million years - albeit they are randomly distributed)
reduced 16% since 1840 (the growth of the South Atlantic Magnetic Anomoly, where there is a weaker field allowing damage to equipment in space)
Around 100k years ago there was a temporary flip, that took place on the scale of centuries, during which the magnetic field weakened by 90%
Although there is no correlation between mass extinctions and polar magnetic field reversals, it could be disastrous for tech!
Which asteroid group forms the majority of Earth crossing and potentially hazardous asteroids
What is the biggest (how big?)
What is arguably the most famous?
Worth noting, its not the biggest near Earth asteroid. Do you know what this is? - what group is it in?
The Apollos
Apollo asteroids are Near Earth Asteroids (NEAs) with perihelion distances less than 1.017 AU, and semi-major axis greater than 1 AU. They have sizes less than 10 km (1866 Sisyphus is the largest discovered so far)
Sisyphus is a binary stony (s-type) asteroid approx. 7km in diameter
Bennu is probably the most famous at present.
The largest NEA is 1036 Ganymed its an s-type asteroid approximately 35km in diameter (so proper big)
It’s in the Amor group
What was the first asteroid (a Mars crosser that might evolve into an Earth crosser - it is classified as an NEA) was the first to be orbited and landed upon by a probe
433 Eros (diameter c.17km)
(of the Amur group)
by NEAR Shoemaker in 2001
So what are the four major groups of Near Earth Asteroids - and how are they defined.
Outer Earth-grazer asteroids are split between Amor and Apollo asteroids.
“Earth grazers” that never get closer to the Sun than Earth does (at any point along its orbit) are Amors, whereas those that do are Apollos.
Inner Earth grazers are called Aten asteroids
Aten asteroids are defined by having a semi-major axis (a) of less than 1.0 astronomical unit (AU)) .
Atiras, are essentially Atens (i.e. within earth’s orbit) that never cross Earth’s orbit (so therefore Atens do!)
So you can see you have inner and outers, and crossers and non-crossers to make up this four!
What is the name of the simple and most well known scale for catagorising asteroid impact hazard (for non-science audience)
What asteroid has the highest rating? (and what comes second)
What is the more complex rating system
Torino scale (note it is limited to impacts in next 100 years)
Apophys - scale number 4
Bennu is number 2, albeit its now a 0. (remember the 100year thing!)
The Palermo Technical Impact Hazard Scale is the more technical one. (Not time limited)
Bennu has the second highest Palermo rating.
