Video 1.5.2: Sedimentary Rock

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我们的地球：气候，历史和进程

85 個評分

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University of Manchester

我们的地球：气候，历史和进程

85 個評分

探索过去的45亿年更好地理解空气，水，土壤和生命如何形成及相互影响

從本節課中

Building Blocks of Earth’s Climate System

Video 1.0: Introduction and Philosophy7:45

Video 1.1: How does science work?6:21

Optional Video: How do scientific papers get published?10:50

Video 1.2: Introduction to the Earth's climate system8:49

Video 1.3: How do we measure geologic time?9:50

Video 1.4: Geological Time Scale Song2:50

Video 1.5: Minerals and Rocks2:59

Video 1.5.1: Igneous Rock3:03

Video 1.5.2: Sedimentary Rock6:15

Video 1.5.3: Metamorphic Rock5:39

Video 1.6: Using radioactivity to date rocks - Dr. Ray Burgess7:48

Video 1.7: Using stable isotopes to understand Earth processes - Dr. Ray Burgess6:15

Video 1.8: How do we know how old the Earth is?5:46

Video 1.9: What are those rocks doing lying around?10:48

與講師見面

Prof. David M. Schultz
Professor of Synoptic Meteorology
School of Earth, Atmospheric and Environmental Sciences
Dr Rochelle Taylor
Postdoctoral Research Associate
School of Earth, Atmospheric & Environmental Sciences
Dr Jonathan Fairman
Postdoctoral Research Associate
School of Earth, Atmospheric and Environmental Sciences

So the second type of rock is called sedimentary rock.

This is rock that is laid down in beds or strata.

So you recognize strata, stratigraphy.

Again, these relate primarily to sedimentary rocks.

There's three or four different types of sedimentary rock.

There's clastic rocks.

These are rocks that are the products of weathering.

So your things like sandstones,

conglomerates, mudstones, these are all clastics.

We have evaporites, these are when minerals are produced

by the evaporation of a warm salty sea leaving the minerals behind.

We have sedimentary rocks that are formed by biological or biochemical processes.

>> For instance, we might talk about the carbonates like the calcium carbonate,

the limestones, these are produced by animals that have shells,

they die, their calcium carbonate shells sink to the bottom and

solidify into layers >> There are also

biological sedimentary rocks that are comprised of silica.

These would be something like cherts, and

these would be microfossils that produce silica shells.

Then the fourth one is pyroclastic flows.

These are flows that are erupted by volcanoes, travel and

are laid down in beds.

Now you can see I've underlined it in blue here,

indicating that it's kind of a hybrid between igneous rock being an extrusive,

erupted from the volcano, but it's also laid down in beds.

So there may be instances where we may see ash deposits that are laid down

as sedimentary layers embedded within mudstones or sandstones.

These ash flows can be critical for dating

the layer of rock because of the isotopes within those minerals.

So here's a small sample of clastic sedimentary rocks.

I've got a conglomerate here, you can see these very smooth,

large pebbles embedded within this matrix of finer grain

sands and this is a very large clastic rock.

Here's another type of large clastic rock.

This is a breccia.

You can see it doesn't have as much matrix surrounding

the individual pieces but these pieces are very angular.

So they haven't had time to erode, as in a stream bed,

such as you might see in this conglomerate.

This is a sandstone here, you all have a sense of the size of sand,

and that's exactly what happens here.

The sand from a beach or a sand dune,

wind blown sand, solidifies and produces these and you can see the layers

of different colored sands within this sandstone.

Here we have either a mudstone or a siltstone.

Here, the individual crystals, minerals are so

fine grained, that you can't see them with the naked eye.

We also have an embedded shell within this fossil

shell embedded within this clastic sedimentary rock.

So here's a different type of sedimentary rock, this is an evaporite.

This, again, is the halite,

the sodium chloride crystals that we saw now in its rock form.

You can see the large size of these crystals as the salty

sea slowly evaporated away leaving the salt.

So here, we are looking at the biochemical sedimentary rocks.

We've got two examples of limestone here.

This limestone is, comes from the Solnhofen deposit in Germany.

This is where they've gotten the Archaeopteryx samples from,

and this is also a limestone, it's much coarser and

you can actually see the individual fossil shells that comprise that.

This limestone is so fine grain that you can't, with the naked eye,

see the individual crystals,

the individual shells of the microscopic animals that have comprised this.

But here, we can actually see these fossils and

how the calcium carbonate shells have been sandwiched together and

lithified to produce this biochemical sedimentary rock.

This is the fourth type of quasi-sedimentary rock, this is a pumice.

This is from an ash flow from a volcanic eruption.

It's very light, it's got very porous structure to it,

where gas bubbles were trapped at the time that this formed.

There's also elements,

small bits of glass here when this ash flow cooled very quickly but

it was laid down in a bed as an extrusive volcanic igneous rock, so

it's kind of this hybrid between a sedimentary rock and an igneous rock

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