TPO 15 Lecture 2 Geology
Narrator:
Listen to part of a lecture in a geology class.
Professor
As geologists , we examine layers of sediment on the Earth' s surface to approximate the dates of past geologic time periods. Ah sediment as you know i s material like sand , gravel, fossil fragments that is transported by natural processes like win d , water flow or the movement of glaciers.
So sediment is transported and then deposited and it forms layers on the Earth ' s surface over time. We examine these layers to learn about different ge ologic time periods including when they began and ended.
For example, from about 1.8 million years ago to around 11 thousand years ago was the Pleistocene epic. The Pleistocene epic was an ice age.
During this epic, sediment was made by the kind of erosion and we athering that happens when the climate is colder, and part of those sediments are fossils of plants and animals that lived at that time.
The Holocene epic followed the Pleistoce ne epic when the Earth ' s climate warmed up around 11 thousand years ago. The Holocene e pic is characterized by different sediments, ones that form when the climate is warme r. Because the climate changed, the types of plants and animals changed also. Holocene sediments contain remnants of more recent plants and animals, so it's pretty easy to diffe rentiate geologically between these two epics.
Now there is growing evidence that the presence of humans has altered the earth so much that a new epic of geologic history has began – the Anthropocene epic, a new human-influe nced epic. T his idea that we ' ve entered a new Anthro-pocene epic was first proposed in 2002. T he idea is that around the year 1800 CE the human population became large enough, around a billion people, that its activities started altering the environment. T his was also the time of the industrial revolution, which brought a tremendous increase in the use of fossil fuels such coal. The exploitation of fossil fuels has brought planet wide developments: industrialization, construction, uh, mass transport. And these developments have caused major changes like additional erosion of the Earth ' s surface and deforestation. Also, things like the damming of rivers , has caused increased sediment production, not to mention the addition of more carbon dioxide and methane in the atmosphere.
Naturally all these changes show up in recent sediments. And these sediments are quite different from pre year 1800 sediment layers.
Interestingly there's some speculation that h umans started having a major impact on Earth much earlier, about 8000 years ago. That's when agriculture was becoming widespread. Early farmers started clearing forests and livestock produced a lot of extra methane. But I want to stress this is just a hypothesis. The idea that early humans could have had such a major effect, well I'm just not sure we can compare it with the industrial age. Geologists in the far future will be able t o examine the sediment being laid down today, whereas right now we can say that yes, human impact on the Earth is clear: It'll be future researchers who have a better perspective and will be able to really draw a line between the Holocene and the Anthropocene epics.
TPO 15
Conversation 2
Narrator
Listen to part of a conversation between a student and her biology .
Professor
Hi Samantha, how did your track meet go?
Samantha
Great! I placed first in one race and third in another.
Professor
Congratulations ! You must practice a lot.
Samantha
Three times a week pre-season, but now that we ' re competing every
weekend, we practice 6 days a week from 3:30 till 5:00.
Professor
Athletics place a heavy demand on your time, don ' t they?
Samantha
Yeah, but I really love competing, so …
Professor
You know I played soccer in college and my biggest challenge, and I didn ' t always succeed, was getting my studying in during soccer season.
Are you having a similar …
Samantha
No, I … I really do make time to study. A nd I actually study more for this class than I do for all my other classes. B ut I didn ' t see the grade I expected on my mid-term exam, which is why I came by.
Professor
Well, you "didn't do badly on the exam, but I agree it did not reflect your potential. I say this because your work on the lab project was exemplary. I was so impressed with the way you handle the microscope and the samples of onion cells, and with how carefully you observed and diagramed and interpreted each stage of cell division. And I don't think you could have done that if you hadn't read and understood the chapter.
I mean it seemed like you really had a good understanding of it. Samantha I thought so too, but I missed some questions about cell division on the exam
Professor
So what happened?
Samantha
I just sort of blanked out, I guess. I had a hard time remembering details.
It was so frustrating.
Professor
Alright, let's back up. You say you studied, where, at home?
Samantha
At my kitchen table actually .
Professor
And that's supposed to be a quiet environment?
Samantha
Not exactly. My brother and parents try to keep it down when I am studying, but the phone pretty much rings off the hook, so …
Professor
So you might try a place with fewer distractions, like the library …
Samantha
But the library closes at mid-night, and I like to study all night before a test, you know, so everything is fresh in my mind. I studied six straight hours the night before the mid-term exam . T hat ' s why I expected to do so much better.
Professor
Oh ok. Y ou know that studying six consecutive hours is not equivalent to studying one hour a day for six days.
Samantha
It isn' t?
Professor
No. There is research that shows that after about an hour of intense focus, your brain needs a break. It needs to, you know, shift gears a little.
Your brain's ability to absorb information starts to decline after about the first hour. So if you are dealing with a lot of new concepts and vocabulary, anyway, if you just reviewed your notes, even 20 minutes a day, it'd be much better than waiting until the night before an exam to try and absorb all those details .
Samantha
Oh, I didn't realize .
Professor
Think of your brain as: a muscle. If you didn't practice regularly with your track team, and then tried to squeeze in three weeks worth of running practice just the day before a track meet, how well do you think you'd perform in your races?
