Transcript TEK 6C and D - Northwest ISD Moodle

(6) Earth in space and time. The student knows the evidence
for how Earth's atmospheres, hydrosphere, and geosphere
formed and changed through time. The student is expected
to:
(c) investigate how the formation of atmospheric oxygen and the
ozone layer impacted the formation of the geosphere and
biosphere
 Diatomic Oxygen
 Oxygen reacts with the iron in the geosphere creating iron
oxide (rust)
 Levels of atmospheric diatomic oxygen and dissolved
diatomic oxygen influenced aerobic life.
 Stratospheric ozone protects terrestrial life from UV
radiation allowing life to flourish
(d) and evaluate the evidence that Earth's cooling led to tectonic
activity, resulting in continents and ocean basins
The geosphere
refers to
everything from
the core of the
Earth to its
surface.
As you can see,
there are many
features within the
Earth that we will
learn about.
The biosphere is the layer of
life on Earth. It exists
beneath, upon, and above the
surface in the atmosphere as
well.
Axolotl
Soil Nematodes
Airborne Bacteria
Harvestman
1. What are some of the Earth’s
features within the geosphere?
2. What is the biosphere?
One thing most geologists
agree on is that the
Earth’s first atmosphere
contained no free oxygen.
There were trace amounts
of Oxygen bound in water
molecules, and Carbon
dioxide…but none of it was
“free”, or molecular
oxygen. (O2)
Photochemical Dissociation Hypothesis states that the sun’s
energy helped the atmosphere evolve through the following
processes:
 The ultraviolet light combined with the water vapor to
set the hydrogen off into space and free the oxygen.
2H2O + UV light energy ----> 2H2 (freed into space) + O2
The newly freed oxygen reacted with methane, forming
carbon dioxide and additional water vapor.
CH4 + 2O2 ----> CO2 + 2H2O
The oxygen also reacted with ammonia, producing
nitrogen and water.
4NH3 + 3O2 ----> 2N2 + 6H2O
Let’s not forget…it was the photochemical
After converting
the ammonia
and methane
to carbon
dissociation
of water
that allowed
the production
dioxide and nitrogen, free oxygen began to accumulate as
offurther
ozonedissociation
(02 + O = O
in our
stratosphere,
of3)water
vapor
continued. which
protected the first cells on Earth.
3. What is meant by “free oxygen”?
4. Besides water, what other molecules play a
vital role in photochemical dissociation?
5. What happens when freed oxygen combines
with methane?
6. What happens when freed oxygen combines
with ammonia?
This theory states that our atmosphere was delivered
to us from the Earth’s interior through volcanic
eruptions. In contrast to the Photochemical
Dissociation Hypothesis, the Outgassing Hypothesis
argues that the free oxygen came from the
photosynthesis of primitive organisms which existed
1.5 - 3.5 billion years ago.
Cyanobacteria
The oxygen took approximately 2 billion years to
become free, but when it did, it formed the ozone
layer, eliminating the dangerous radiation and setting
up the foundation for a habitable planet.
It is obvious that Earth
contains O2 now, and without
it, aerobic life would not be
possible.
What life could have evolved
all those billions of years ago,
before there was significant
O2 in our atmosphere?
Anaerobic life forms
http://www.teachersdomain.
org/resource/tdc02.sci.life.ce
ll.stetteroxygen/
Although the early Earth was mostly
devoid of molecular oxygen, high
volcanic activity released significant
amounts of molecular hydrogen.
With little oxygen available to
convert that hydrogen into water,
hydrogen gas probably accumulated
in the atmosphere and oceans in
concentrations as high as hundreds
to thousands of parts per million.
Thus, the early Earth was likely a
paradise for methanogens
(methane-producing bacteria) that
fed directly on hydrogen and carbon
dioxide, at least until the
atmospheric hydrogen was depleted.
7. What primitive organism uses photosynthesis to
combine CO2 and water in the presence of sunlight
to make sugar and O2?
8. What are methanogens, and why was early Earth a
paradise for them?
9. Where did these methanogens retreat to, when
oxygen started evolving in our atmosphere?
10. Where did the molecular hydrogen of the Earth’s
first atmosphere likely go?
Many anaerobic microbes including methanogens are easily
poisoned by oxygen, and the recent discovery of banded
sediments with rusted iron suggests that oxygen-producing,
photosynthetic microbes called cyanobacteria were able to
gather sunlight for photosynthesis. These BIFs would not
have formed without O2 present in the atmosphere. Because
the ocean is now oxygenated all the time, iron can no longer
dissolve in sea water. Instead, it precipitates out as iron oxide.
The evolution of O2 in our
atmosphere spelled doom
for the proliferate
methanogens, and other
types of extremophiles that
had evolved during this early
period in Earth’s past. This
led to the GOE…Earth’s
greatest extinction event.
Despite their small stature, one of
the first aerobic organisms (require
the presence of O2) set in motion a
process that would change everything.
These cyanobacteria which evolved
3.5-1.5 billion years ago (also known as
blue-green algae), were remarkably
self-sufficient creatures that could
use the sun’s energy to make their
own food, and fix nitrogen, a process
where nitrogen gas is converted into
ammonia or nitrate. (NH3; NO3)
While this may not seem significant, the cycling of nitrogen on Earth is
essential for life. It is found in amino acids, proteins, and genetic material.
Nitrogen is the most abundant element in the atmosphere (~78%).
However, gaseous nitrogen must be 'fixed' into another form so that it can
be used by living organisms.
11. How did banded iron formations
form…and why can’t they form
anymore?
12. What does it mean to “fix” nitrogen,
and why is this process so important to
life on Earth?
And then...nothing else happened. At
least, not for another two billion
years!
It wouldn't be until about 600 million
years ago, that the first multicellular
organisms finally emerged.
So what happened during that
immense, multi-billion year gap? Why
did it take so long for more complex
life to arrive on the scene?
For that matter, why did oxygen suddenly spike 2.5 billion
It may have been volcanic
years ago?
outgassing, followed by
The simple, uncomfortable answer is
photochemical
dissociation…or
that we don't really know.
photosynthesis. Or all three!
??
When rain falls, it is freshwater. H2O, which
condenses on a nuclei aerosol (tiny dust particle).
When rainwater falls on the solid surface of the Earth, it
moves ultimately towards the oceans, through gravity. On the
way, streams and rivers form.
Over the millenia, water erodes and weathers the surface of
the Earth, and carries with it, many minerals on its journey to
the ocean. Salt is the main mineral it carries.
We already know that over time, the Earth’s
crust cooled. The crust is thin, relatively,
varying from a few tens of kilometers thick
beneath the continents to less than 10 km
thick beneath the oceans.
The crust and upper mantle together constitute
the lithosphere, which is typically 50-100 km
thick and is broken into large plates. These
plates sit on the asthenosphere.
The asthenosphere is kept plastic largely
through heat generated by radioactive decay.
This heat source is relatively small, but
nevertheless, because of the insulating
properties of the Earth's rocks at the surface,
this is sufficient to keep the asthenosphere
plastic in consistency.
13. Why was there a huge 2 billion year gap
between the first origins of life and oxygen in the
atmosphere, and the appearance of more
complex life forms?
14. Of what two layers is the lithosphere
composed?
15. How is the asthenosphere kept plastic?
http://www.youtube.
Energy can be transferred
in three ways…
com/watch?v=p0d
across the vacuum of space
 Radiation Energy transfer
WF_3PYh4
 Conduction Energy transfer directly from molecule to molecule (solids)
 Convection Energy transfer through fluids (liquids and gases)
Very slow convection currents flow in the asthenosphere,
(upper portion of the mantle) and these currents provide
horizontal forces on the plates of the lithosphere much as
convection in a pan of boiling water causes a piece of cork
on the surface of the water to be pushed sideways.
16. Name and describe briefly
three ways that thermal energy
(heat) can be transferred, and
give examples.
17. How do convection currents
drive tectonic plates?
Of course, the timescale for
convection in the pan with corks is
seconds and for plate tectonics is 10100 million years, but the principles
are similar.
Differentiation
within the Earth is
crucial to plate
tectonics, because
it is responsible for
producing an
interior that can
support tectonic
motion.
The heat generated by the
lower mantle, drives the
convection currents upward
against the lithospheric
plates.
As the currents cool, they move laterally, pushing and pulling the lithosphere apart.
Then, as they cool, the currents move downward again, where they begin to heat up
once more due to proximity to lower mantle heat.
While seemingly static, the geosphere is in fact a very active
player
in the
Earth
systems,
affecting the atmosphere and the
Remember
also,
that
these dissolved
hydrosphere,
asform
well as
processes
such as the
minerals in the
of critical
salts, may
be
hydrologic
cycle and
other biogeochemical
cycles.
carried through
weathering
and

The types
ofseas,
minerals
contained
in soils--a factor of
erosion
to the
making
the
geologic
processes--help
to determine
the vegetative cover
oceans salty,
so the geosphere
can
and
ecosystems
at the surface.
affect
the hydrosphere
in that way as
well.
 Carbon – an essential element of life – is bound in organic
matter and is carried to the ocean via wind and water erosion
where eventually it becomes part of the ocean floor.
Tectonic movement carries the ocean deposits into the
Earth's interior. On geologic timescales, volcanic activity can
vent the carbon to the Earth's atmosphere as carbon dioxide.
The carbon cycle is one of
the key cycles linking the
Earth’s subsystems:
geosphere, atmosphere,
hydrosphere, and biosphere.
As a reminder, the outer core of the Earth contains liquid iron.
Its motion is thought to drive the Earth's magnetic field – the
magnetosphere - which extends far beyond the atmosphere
protecting Earth and its biosphere from solar wind and cosmic
radiation.
From the time of
Pangea, to
current, this
animation
represents how
Earth’s plates
have changed
(from 270 mya to
200 mya)
Being dynamic, the Earth is still changing. 150 million years in the future,
the continents should look something like this.
In 250 million years, we will have another Pangea-like supercontinent,
called Amasia
18. How does the geosphere influence the
biosphere, hydrosphere, and atmosphere?
19. Why is Earth’s outer core so important?
20. Because the Earth’s tectonic activity
keeps the surface ever-changing, how long
do scientists predict it will take before there
is another supercontinent?