Geology & the Earth
The Earth consists of a series of nested layers. Deepest, of course, is the core. We
do not have any direct samples. We can only examine the core of the Earth using
remote sensing. Geophysical techniques. What we know about the course suggests
that number one, the core, is primarily made out of an iron nickel alloy, perhaps
himself rat. And there's two parts to the core, the outer part of the core is actually
liquid. The inner part of the core is a very high pressure metallic solid. The core,
the inner core is basically greased up by that liquid outer core, and so the inner
core is free to spin. Irrespective of what the rest of the earth the overlying portions
of the Earth are doing, an it's that spin that incidentally generates the Earth's
magnetic field. Above the core we have the mantle. And above the mantle we have
two layers that are broadly referred to as the asthenosphere and the lithosphere.
The asthenosphere is. This is the zone. In the mantle that is relatively. Plastic, it's
under high pressure, not nearly as high pressure is the core, but it's still that
largest zone in the interior of the earth that is relatively plastic because it's under
high pressure and it's capable. Because of that, it's capable of flowing from one
place to another.
The lithosphere, which is the outermost part. Of the Earth, solid earth, the left fear
is approximately 150 kilometers thick, and it is relatively rigid, the. Lower part of
the lithosphere is generally considered to be part of the mantle. The upper part of
the lithosphere is considered to be a separate zone that I'm sure you've already
heard referred to as the crust of the Earth. Now the lithosphere, the uppermost
rigid part of the mantle, plus the crust. The lithosphere is divided into a series of
separate physical plates and those plates are capable of moving relative to one
another, moving over the surface of the Earth. New plate material being produced
in certain parts of the Earth. Old plate material being consumed shoved back into
deeper parts of the mantle. By other processes, other places on the Earth, and so
the lithospheric plates there was about between. Depending on how you count how
big you want to define each plate on the order of a large dozen to maybe 20 plates
that are jostling around the earth surface and the part of the earth, the solid earth
in the year most familiar with are the continents, and these continental masses.
Are embedded within the uppermost part of the lithosphere and as the plates move
around, they carry the continental masses with them. And so as a process that used
to be referred to as continental drift, that name has been dumped. When one
theory was replaced by another, will talk about that later. Continental drift when
there was a theoretical shift in the earth sciences, got renamed instead, plate
tectonics and it play tectonics is a central theory that unites the earth sciences
together and we'll talk a lot about plate tectonics later, but plate tectonics once
again involves the movement. Of lithospheric plates overtime and in the process
carrying continental surficial continental masses. Mountains and all along with
them. Before we go into any kind of detail in terms of geology, the structure of the
earth or plate tectonics, it's appropriate to talk for a moment about the scientific
method now. Every educator, every science educator have ever talked to has to or
they feel obliged to present their view of the scientific method an I suspect that
there are more detailed definitions of the scientific method. Then there are even
educators who teach this stuff. The that's the reason for that is that each scientist
has their own view, their own personal take on how science works for them with
their research and their personal career. But if you stand back and don't worry
quite so much about all of the detail that you learned in earlier science classes. The
scientific method consists First off of observations, facts you make observations on
the real world. And you strive as a scientist to make those observations as accurate
as unbiased, an as repeatable by making multiple observations on the same on the
same phenomenon. Once you have these solid and I should add well documented
facts. Then you attempt to explain why you seeing what you've seen. That's the
second part of the scientific method. First one is making good solid. The best you
can make observations. And the second is come up with an idea. A hypothesis to
explain what you've seen. We don't stop there. What makes science unique among
intellectual disciplines? Is that we then skeptically test our explanations. We
skeptically attempt to reject each hypothesis. That potentially explains what we
saw. And now that that test does not mean oh want to think about it and come up
with some sort of a test, some logical test it means. Let's predict from our ideas.
Let's predict what we'll see if we make more observations and each hypothesis,
each idea. Each hypothesis will allow us to predict different critical observations
that we could make if we fail to make those observations. If they don't exist when
we try and make new observations then we reject that hypothesis, and so, by
critically and very skeptically testing every idea that we can come up with the
explain what we saw originally. Then we eventually are able to reject the
hypothesis. They might be good ones, but they're just not accurate an. Ideally, if
the scientist is doing his or her job properly ideal you will end up with a single
hypothesis in the end, and that's that. That's the one that we present. Now, science
doesn't stop there. Science starts with observations. Generate ideas, hypotheses to
explain those observations, and then skeptically critically tests attempts to reject
each one of the hypotheses. And still we end up with just one hypothesis. But we
but science we as scientists. Go through this process skeptically, testing with new
observations over and over and over again. The process never stops. Science is
capable of disproving ideas we are not capable. On the other hand, approving them,
and so since we can't prove an idea, best we can do is find supporting evidence for
it. And failed to reject the hypothesis, so there's always room for more testing. And
maybe one scientist gets tired of testing after while they say, OK, OK, I've tested
this idea 20 times and I keep on getting the only the only idea that survives is this
one. I keep on getting the same answer, so I'm done, but somebody else
undoubtedly will come along and say I think you didn't make enough observations,
or I've got a new way of making observations. I have a new way of testing or I've
come up with two hypotheses you didn't think of, and I got those two, and so when
additional scientists come along, they more than likely will continue to test the
surviving hypothesis that once have been rejected previously. And it's in that
fashion that scientists come up with overtime more and more and more evidence
that supports. A particular idea at some point. We stop saying. OK, I'm going to test
this some more. We say well, tentatively I'll accept it and it's at that point that
hypothesis becomes more established and we often refer to it. Then as a theory,
that's a scientific method. The court to it is accurate, repeatable observations.
Don't just take one story, do it over and over again to make sure you're doing right.
Record the information and it depends upon ideas explanations. But then science
also depends upon being very skeptically being very skeptical, rather and then
testing your ideas and try to reject them. Tries hard as you can to reject them.
Based upon new critical observations. So once again, facts ideas, skeptical testing
to try very hard to reject hypothesis. Most of those hypotheses have been rejected.
You start all over again, make more skeptical tests, more observations, and keep on
going to see which hypothesis survives and said never ending process. At some
point when we finally call hypothesis theory, which is pretty much a consensus.
That yeah, I think we're right, at least for the time being. We always go back and
check it again, but more than likely most scientists are going to move on and that's
the nature of science.
For most of the time that geology has existed as a science, that is since early in the
lady early in the 1800s. We have tried to each generation focus more and more and
more narrowly on a wider, wider, wider range of topics. Of course, that means, as
it progressively greater number of geologists every generation, and by focusing in
narrowly we have the time we have the concentration, we have the opportunity to
learn more about our own little area. That process is tended to fragment, which
has fragmented science and has tended to fragmental subdivided the geology into
structural geologists. People who study rocks, people who study landforms, people
who studied the oceans, people who studied the way that that chemistry produces
different kinds of earth materials, the way that we remotely stance using
geophysical information to see what's down there, for example. And in the last 30
years or so, geologists start to become concerned by this. This subdivision of the
earth sciences, because as paleontologist, perhaps you don't know as much about
the interior of the earth as you ought to know, and so there has been this.
Educational effort, referred to as the Earth system concept to try and re integrate
all of the various parts of the earth sciences into a single coherent view and that
effort to resynthesize, to reintegrate all of the different parts of geology is once
again referred to as the Earth system concept, and your textbook was written. With
that Earth system concept in mind, and so you will notice, it may seem like the
discussions are a lot broader when you get to the chapter on structural geology
with my God, there's some discussions of physics. There's some discussions of
geophysics. There were some discussions of rock types in there, list some
discussions of mineralogy, and that's not just throwing stuff into confuse the
introductory student. All that information is thrown in and discussed under the
concept of structural geology to let all of these various pieces of information get
integrated and to demonstrate to students that it is a whole coherent topic that
we're studying not just an individual little bit of fold or an individual little bit of
convection in the mantle, or something like that. So the Earth system concept has
been representing major shift in geological education and your book is clearly
established as a major effort. To teach students to teach this present generation of
college students geology as an integrated Earth system discipline.
In the nucleus of an atom we have two fundamental particles and this has been
known for well over a century or two. Fundamental types of particles. There are
particles that have a positive charge on them, which are referred to as protons and
the number of protons in a nucleus. The other particles are neutrons, and neutrons
have no charge on them. But they have roughly each neutron has roughly the same
mass proton, and so the bulk of the mass of an atom. Is the mass of the total
number of protons and neutrons. In the nucleus, the lightest way element and that
one with the smallest atom is hydrogen, where there is only one proton an. Zero
wow one, two, or three. Neutrons. Hydrogen has an atomic number of 1 because
it's got one proton and every atom of hydrogen. Has one proton in it and that
proton is the is the charged part of the nucleus at one proton you got one unit
charge of positive. And so that's balanced by the number of electrons. Even though
electrons have virtually no mass, they nonetheless carry a charge, which is about
the same size as the charge on a proton, except in electrons.