I alluded in YEC part 2 that I didn’t believe the Phanerozoic fossil record (supposedly 500 million years ago) could stay intact since an erosion rate of 2.5 microns per year would erase a lot of it. There is a related complication.
Perhaps a picture is worth a thousand words. Below is depiction of the layers around the Wytch Farm Oilfield.
The bottom layer is the Sherwood Sandstone claimed to be in the Triassic (250 to 200 million years ago) and the top layer of Greensand claimed to be in the Eocene (56 – 33.9 million years ago).
You’ll notice that the layers are bent together, suggesting the layers formed one on top of another. No argument there. But this suggests they had to form with no geological interruption from 250 million years ago to about 34 million years ago or whenever the fault happened that caused all that bending of the layers together.
How long and to what extent do defenders of Old Fossil Record geology claim stasis must lasted so that all those layers can form relatively undisturbed? 250 million years? If we find those kind of stratified layers going miles and miles, why do they remain undisturbed for 250 million years and nicely build up like a layer cake before getting bent and sheered out of shape suddenly? Anyone really believe it was so calm and collected for 250 million years to allow the layers to form nicely on top of each other?
Where do the sediments come from, and why are the contact domains so nice and smooth so there are nice discrete changes in color between strata? The sediments came from where? And why the sudden changes in color?
I used to be an Old Earth Creationists until I pondered such diagrams, then I became skeptical, and then with the examination of other evidence, I no longer found it possible to believe the fossil record was old.
And finally you can see for yourself how the “layers” are really laid out — horizontally! The Cambrian sometimes is almost at the same elevation as the Cretaceous. So did the layers nicely form on top of each other for 500 million years before getting bent like a bent out of shape so that they get represented horizontally?
When did all those nice outcrops form such that we can see the Cambrian at the same elevation as the Cretaceous? Something about the claimed ages doesn’t agree with these diagrams.
Something is amiss.
Photo above from :
http://www.southampton.ac.uk/~imw/jpg-Petroleum-Geology/10PTS-Lulworth-Wytch-Structure.jpg
Sal:
But this suggests they had to form with no geological interruption from 250 million years ago to about 34 million years ago or whenever the fault happened that caused all that bending of the layers together.
Your diagram mentions Middle Eocene and other unconformities not shown, what is the yec explanation that makes more sense?
You have no doubt given this years of study. So what is the official explanation and why do you disagree?
Sal,
Yes, have you worked it out yet? HINT: It’s you.
Are you really so ignorant that you’ve never read about plate tectonic forces and how geologic unconformities are formed?
Wow.
Sal, this is not the first time you have asked about erosion rates. Please go back to the thread where this was answered.
I’m glad that you are looking at some mainstream geological articles.
Rather than pose a problem for an old earth, I put to you that what you are showing poses unsurmountable problems for a young earth.
If you read up on the geology of NW Europe you will find that large areas have been stable for a long period of time, essentially between the Late Carboniferous and the early Tertiary. During most of this time this area formed part of what is known as Laurasia: the Northern part of the super-continent of Pangaea that was formed at the end of the Hercynian orogeny. A nice site to see the plate reconstructions throughout geological time is this one
These reconstructions are of course a high level synthesis of many, many earlier studies. The kind of data that goes into these come from all over the geological sciences: stratigraphy, sedimentology, paleontology, structural geology, paleomagnetism, paleo-climatology and many more. It is a fascinating to see scientists compile so much seemingly independent data and to watch the overall picture grow and come together. Make no mistake, this work has taken many decades to get to this stage and it is by no means finished.
Anyway, during the Mesozoic this area was part of a huge continental mass, far away from plate boundaries and areas of tectonic activity. Stable in the lateral sense, it was nevertheless undergoing continuous, relatively small vertical movements of the continental crust, and was also impacted by fluctuations in sea level. This interplay caused periods of emergence to alternate with periods of drowning. Basically it was part of a stable continental shelf for long periods at the time. Coupled with the gradual movement of this land mass from near the equator to the higher latitudes (as evidenced by paleomagnetic data) this causes a lot of variation in the depositional environment, which is reflected in the nature of the rocks.
Further to the South an ocean had opened in the early Mesozoic, known as Tethys. This more or less separated what is now Africa from what is now Europe and Asia. Towards the early Tertiary, differential plate movements caused Tethys to disappear as the African plate collided with the Eurasian one. The plate boundary was caught in a vice and strong deformation resulted in the formation and the uplift of the Alpine mountain chain. Although Great Britain was relatively far to the North of this, it did get affected in a minor way by the ripples of this great orogeny. The deformation in the picture you showed is caused by this.
The British Isles as a whole have undergone a gradual tilt from West to East, causing progressively older rocks to outcrop as you go from the East Coast to Wales and NW Scotland. This has been known since before the time of Darwin.
I am not just making all this up – this knowledge is derived from two centuries of work by generations of earth scientists. I have referred you before to the books by Richard Fortey, I can recommend them as an introduction for laymen.
Mainstream geology has a narrative that pulls together all the tons of data into a consistent and coherent story. Nothing that is claimed contradicts with the basic laws of physics and chemistry, nor with biology as we know it – but it does take hundreds of millions of years to produce the rocks and structures you are looking at. Nothing is amiss. For instance there is consilience between the paleomagnetic data that tells us at what latitude these sediments were deposited at any given time, and the prevailing paleoclimate as evidenced by the sediments. The fossils in these rocks are sorted very finely in the vertical sense, and they form an orderly progression that reflects the development of life on Earth during these 250 million years. This order is so well expressed and understood that we can use outcrop data from the Southwest to predict the fossils we will find in corresponding intervals in wells in the North Sea, hundreds of miles away.
Do you have a physically/chemically/ biologically/geologically sound story that explains how all this could be formed in a mere few thousand years?
fG
Sal, can you explain why you drop out of discussions where your questions have been addressed, and bring them again as if the previous discussion never happened?
Looks like we need a new thread then to collect all the questions Sal has ignored in his old threads.
By the way, Sal, you are now getting quite close to Glenn Morton .
He was a YEC until he started to work as a geophysicist in an oil company and got to see the data first hand. He discovered that the reality is utterly incompatible with the YEC stories, and he turned OEC.
Think about that for a moment.
fG
Why are their miles of sediments (including sedimentary rock) in the Gulf of Mexico? Could it be because basins tend to get filled, and not to erode themselves?
As the sediments accumulate, the whole mass tends to sink, keeping the basin from becoming “filled” any too quickly.
How soon should we expect the sediments in the Mediterranean Sea to start eroding? Great Lakes?
The African Rift Valley is a great place to look for fossils of our ancestors, because it fills with sediment, rather than eroding. It’s been filling with sediments for a long time, both because of subsidence due to the weight of accumulated sediments, and because rifting constantly keeps the valley low.
It’s really not a mystery that lower areas can infill with sediments for a long time, if sometimes disrupted by uplift to produce unconformities. Where does so much material come from to keep infilling such large areas? Uplift elsewhere. Where did the Appalachian Mountains disappear to, or so much of the Rockies, even?
You end up with uplift that persists for 10s or 100s of millions of years, due to converging plates, and what are you going to get on the leeward side? 10s to 100s of millions of years of sedimentary deposits. It’s really rather obvious.
If Sal would actually answer questions, rather than posing the same answered “questions” over and over again, he might start to confront what really happens. As I noted previously, the older cratons of the earth often have the roots of mountains visible within them. What is supposed to happen to all of that material? It has to be deposited somewhere. Most of the sediments that were deposited have indeed eroded since then, as uplift and subsidence change and shift with plate tectonics, but there’s always some that manages to remain in the vast areas of (mostly) deposition, at least.
What a YEC needs to confront is how much more prevalent younger sediments are than older ones. Cambrian sedimentary rocks are indeed not nearly so common as Cretaceous sedimentary rocks, and Ediacaran fauna aren’t found in many places. Back by the time of the Archaean Era, sedimentary rocks are quite rare, and the Hadean just yields a few zircons that survived. Of course sedimentary rocks tend to disappear over time, but often there are huge stacks of sedimentary and sometimes igneous rocks atop the older rocks, and, by the time these erode away, deposition is occurring again in some places. In others, like with the Burgess Shale, yes, Cambrian rocks are being destroyed.
Glen Davidson
Sal, now that this question has been answered for the third or fourth time, can we expect you to come back in a month or two with the same question?
Petrushka,
The YEC 1 and YEC 2 were insufficiently focused. I’m trying to collect pro and con in highly focused technical discussion to make them manageable.
And no, my objections weren’t addressed. People brought up Uranium contamination as a mechanism of C14, and then I demanded what they believed were appropriate Uranium concentrations — this after I even showed a mainstream peer-reviewed article that rejected Uranium/Thorium as an adequate contamination mechanism. No adequate replies. Glen through in inorganic contamination, which was rather uninformed given that inorganic implies carbon free, and therefore would actually help my case since it would dilute rather than concentrate the C14. And no one even touched racemization dating issues. At some point, I just don’t bother with people who put up counterpoints that aren’t really well thought out. It may give the impression I didn’t have an adequate counter when in reality, I thought it trifling so I didn’t bother.
In contrast, faded_glory has given some of the best counter viewpoints to mine. And rather than readers reading Joe-G-type shouting matches, I’d like to give fg a chance to showcase his opposing viewpoints. This will happen when a specific geological feature and question is examined, rather than relatively vague overviews.
I’d be very happy to discuss fg’s insights to some of my YEC colleages who are professors of Geologly (like Marcus Ross, John Whitemore, Timothy Cleary). These YECs are aware of the problem in the YEC model and have communicated the issues to me as well. On the other hand, there are serious issues with the OLD Fossil model, to my mind, likely fatal.
I’m extremely grateful for fg’s contribution to this discussion as it appraises me of difficulties in the Young Fossil Record (YFR) model. This is a great opportunity to hear the viewpoint of a professional in the petroleum and geological industry. Few times in the ID debate do we even get to explore this stuff.
Notwithstanding your reasonable complaint, I hope threads like this which are more focused will make amends as you’ll get to hear both sides go into technical details. Unlike the shouting advocacy forums, with respect to geology, I’m quite happy to receive highly critical viewpoint from informed professionals in their field.
Many thanks to faded_glory for his participation. He has substantially more knowledge about geology than I, and I don’t want to take anything away from his expertise by expressing my opposing viewpoint.
Deal with it as it was. I only mentioned inorganic sources as a possible supplement to legitimate processes that someone else had brought up, not as the only source for, yes, uranium (not C14–I already answered your pathetic objection, and you just repeat it).
Since it was about uranium which can transform N14 into C14, your “objection” is completely off of the mark. Deal with what was written, rather than with your continued ignorance of what’s at issue.
Glen Davidson
Laughable.
Of the two, which is better supported?
That’s not the issue, it’s the long stasis required to form the CONFORMITIES and the ratio of unconformities in higher strata vs. lower strata (should have substantially more than higher strata).
The other issue is the correlation of fossils to certain kinds of stone. If there is tons of erosion of other geological regions (like mountains that supposedly contain sediments from older layers) the fossil correlation with stone should not be so great. As I said, an issue is why the strata are stratified with nice discrete changes in contact zones along with fossils to boot. I’d expect to see more non-correlation in supposed fossil “evolution” versus sedimentary type since supposedly techtonic uplifts are providing sediments from older layer strata to form new strata.
The orderliness of with the fossils with certain sediment types is problematic for a slow geological formation of the fossil record. And finally, for well-preserved land fossils, how do you think they got buried, fast (as in minutes to weeks) or slow (thousands of years)? If you say slow, that’s falsified because burial must be fast, if you say fast, then why do we need to argue the record is necessarily millions of years old? Checkmate.
Oh I see, major issues like the erosion of vast mountain systems is just so trifling that you object to inorganic sources of uranium, as if the source of C14 itself was being discussed.
And the matter of rocks that would take millions of years to cool–and that happen to be cool? Who needs them?
No, you ignore extremely pertinent facts in order to harp on a few questions. That’s not following the evidence, it’s picking the evidence over to fit your preconceptions.
Glen Davidson
Glen,
Inorganic implies carbon free, remember that. 🙂
Should the original source for uranium be expected to be organic or inorganic?
Can you figure that out, Sal?
Glen Davidson
What % of living things leave a fossil? Would you care to guess?
Let alone, how many land anmals leave well-preserved fossils? Bits and pieces of dinosaurs are the typical dinosaur finds.
Glen Davidson
By the way, not that it really matters to what I was writing, “organic” by no means implies “carbon free.” Another bit of ignorance from Sal.
Charcoal, CO2, carbonates, diamond, etc., are inorganic carbon-containing substances. Charcoal is one inorganic carbon source that may have substantial C14 in it, like CO2.
Glen Davidson
Not as pathetic as thinking silicon dioxide (aka silica) can increase C14 content because:
1. it has no carbon
2. it has no Uranium or other comparable radiogenic sources
Something Glen can’t seem to appreciate since it was Glen who said:
FYI:FTR
https://en.wikipedia.org/wiki/Silicon_dioxide
There is no carbon nor Uranium in a substance that has the chemical formula SiO2. 🙂
Thank you for your compliments, Salvador. I do think it is a nice change to see you dig out some actual geological work to discuss and it is always fun to look at some rocks. However, that doesn’t mean I am here at your beck and call to jump with you on any old merry-go-round you might bring up. There is also no need to fawn over me, I am certainly no Geology Big Shot but just a (retired) oil industry geo-professional, and my expertise is not really all that broad. Besides, for the last 10 years I have been busier with budgets and man-management than with the Earth Science! There are obviously other posters here who know quite a bit about Geology so no need to single me out.
I am actually not sure what you are trying to achieve with these threads. The blog format is not the right medium to get into the nitty gritty of the science. I don’t mean this in a disrespectful way, but to educate you to the point where you are less confused about the very basics would take an inordinate amount of words. We can’t do that here. Why do you think there are so many voluminous text books? Geology is a very extensive, quite old science with ginormous amounts of data and studies from all over the world. It can’t all be explained in a couple of paragraphs.
If you really are interested in what Geology can tell us, you should enroll in some Uni courses – proper ones, not ICR rubbish. You are smart enough to get through those easily – if you set aside your obsession with proving everybody wrong about the age of the Earth, or the fossils, for the time being. Just get a feel for how the planet actually works, what it may have looked like in the past, and how we can know all that – and then marvel at how it forms the very stage on which the drama of Life plays out.
Once you get your head around that, many other things will become clear soon enough. The principles, tools and techniques are not all that complicated and for someone with a physics background easy to grasp. Geology is rock science, not rocket science!
fG
You never addressed the oft-repeated issue of uranium deposited in coal from groundwater. None of your references addressed that.
Yeah, you didn’t reply to the adequate replies at all except to repeat irrelevant assertions.
Mostly you. You did not produce any evidence or discussion of any racemization dating issues, you asserted issues.
Well, we continue to bother with you, who never thinks out your posts. Witness the fact that you so consistently misunderstood the uranium-in-groundwater issue that it’s really hard to believe your avoidance is not intentional.
I didn’t say that silica increases C14 content. Deal with what I wrote.
What does “other inorganic matter” mean, Sal? Does it mean SiO2?
What does “other inorganic matter” mean, Sal? Does it mean SiO2?
Your reading comprehension is abysmal.
Glen Davidson
Here’s another one I didn’t respond to because it’s in the category of whiney:
Here is a Paleocene Sandstone (around 66-56 MYO supposedly). Sandstone is a rock, there are fossils buried in that rock.
http://pubs.usgs.gov/of/2008/1228/
Adapa’s point refuted by hard evidence. There are fossil’s buried in rock.
And the notion of fossils buried in sandstone (rocks) is used outside of this discussion:
http://articles.latimes.com/2008/jan/15/local/me-fossil15
Doesn’t matter that minerals were there to replace parts of the fossil since the strict definition of minerals is inorganic and the loose definition that includes carbon would still become C14 free over time. Whiney comments that aren’t
even on target.
Since the comment was made that I didn’t address it, that’s part of the explanation. JonF invoking Uranium contamination and completely dodging the issue of requisite concentration is another example, especially bad since the OP of YEC Part 2 even gave peer-reviewed reference that dismissed Uranium as mechanism capable of creating the detected trace levels of C14.
Appreciate the effort to respond, but such erroneous and substance-free commentary doesn’t further scientific understanding.
Take that to heart.
And quit whining all of the time when people get the better of your substanceless complaints and complete lack of evidence for your claims.
Glen Davidson
Actually the blog world discussion sparked my interest in more science education several years ago even though I was slowly migrating into private investment management. So my education was painfully not that relevant to the job except for sharpening my math. These discussions are an extension of my thought process.
It was hard going back for my last degree (engineering related physics). I’d like to learn more geology personally.
Unfortunately, my academic sponsors are pointing me toward chemistry and biophysics. Not enough hours in the day to explore even a fraction of what is out there.
Btw, hope you’re enjoying your retirement!
I have a really hard time to figure out what you are trying to say here. When you say ‘correlation of fossils to certain kinds of stone’ what do you mean exactly? I presume you have no quibble with fossils being by and large confined to sedimentary rocks (or rarely preserved to some degree in low grade metamorphic rocks, or buried in volcanic ash (re. Pompeii!). Assuming you are pointing to some kind of correlation between certain fossils and the type of sedimentary rock they are mostly found in, this is quite logical. Both the rocks and the organisms are products of their environment. You won’t find dinosaurs in deep oceanic oozes and you won’t find marine shells in desert sediments.
I don’t see what erosion has to do with this. Sure, erosion generates the raw materials to form sandstones and shales (known as ‘clastics’), but these materials are transported and re-deposited in particular environments where particular organisms live and die. Source material is important, but just as important for the eventual rock type are the characteristics of the depositional environment such as energy levels, proximity to sea level, geological stability, climate.. things like that. These very same factors have a major influence on the type of organisms that live in a particular environment, and therefore may become fossils.
On the contrary. What YEC’s need to explain but singularly fail to do, is why the fossil record is so comprehensively and delicately stratified. What causes the near perfect sorting of fossils in the vertical (time) sense, by and large independent of their size, shape or makeup? This, and the radiometric dating results, are the two most devastating individual arguments against a young earth. The beautiful consilience between widely different data (such as paleomagntism and paleoclimate, but there are many others) provides the knockout blow.
Burial would generally have to be rather fast to preserve the remains. However, the argument for the old sedimentary record is not based on burial rates of fossils.
One of the first geologists to appreciate the enormous amounts of time that the geological record represents was James Hutton. He came to this insight when he sought an explanation for the spectacular unconformities like the one at Siccar Point.
The rocks at the base were deposited, lithified, tilted, exposed and eroded before a new cycle of sedimentation started all over again and deposited the flat layers on top. Hutton correctly concluded that cycles like these would take many millions of years*. He came to this insight in 1788 – a whopping 71 years before publication of On the Origin of Species.
fG
* “Gently sloping strata of 345-million-year-old Devonian Old Red Sandstone overlie near vertical layers of 425-million-year-old Silurian greywacke”
faded_Glory,
William Smith deserves a mention, too.
I’m still baffled why Sal and other YECs consider these contra-factual beliefs important. God loves you, Sal, whether you are sucked into these myths or not.
Sal said:
“And finally, for well-preserved land fossils, how do you think they got buried, fast (as in minutes to weeks) or slow (thousands of years)? If you say slow, that’s falsified because burial must be fast, if you say fast, then why do we need to argue the record is necessarily millions of years old? Checkmate.”
I admit I don’t understand this. It’s like saying that people die quickly, and THEREFORE people can’t have died a long time ago! How does the rate at which something was buried, relate to WHEN that event occurred? Is there supposed to be some rule that if something was buried in seconds, therefore that burial must have happened recently?
Pretty much everything you post is in the category of mind-numbingly stupid Sal. Because *some* fossils are found in sandstone doesn’t mean that they *all* are.
I notice you tucked tail and ran from the multiple people who pointed you to deformed fossils like the stretched and skewed trilobite found embedded in slate
deformed trilobite fossil in slate
Who buried that one Sal?
Your ignorance of the most basic scientific facts would embarrass a 10 year old.
Salvador pretty much evaded the question of the Bible in his previous YEC threads, and I have to wonder why. Everyone should wonder why.
Here is a statement that probably no YEC would disagree with:
Truth cannot contradict truth.
Here is another statement that a YEC may well disagree with:
“Now truth as it involves religious belief is something else again, for this truth does not come simply from reason, as does scientific truth, but from faith. Yet since truth is one, and does not admit of internal contradiction, the truths of faith go beyond, but cannot go contrary to, truths demonstrably obtained by reason.”
Not that truth does not admit of internal contradiction, but that the truths of faith cannot go contrary to the truths of reason [scientific truth].
YECism is heavily tied in to the belief that the Bible is literally true. Scientific truth cannot contradict “bible truth.” Therefore science must be wrong [not true]. It’s all very logical. But wrong-headed.
If it were not for this belief, and as far as I know it is what ties all YEC’s together, there would be no sound reason at all to be a YEC.
Well, there you have it, my attempt to give you a glimpse inside Sal’s head, for what it’s worth, since he doesn’t seem to want to discuss it.
I can’t recall to what extent my own realization that everything in the bible wasn’t intended to be taken literally changed my own thinking about the whole YEC thing, but it has had profound impact on other beliefs [no, Jesus isn’t coming back in 1988] without any corresponding loss of faith or abandonment of reason.
There’s hope for Salvador too.
That said, my opinion is that Salvador prefers to focus on these non-essential details rather than focus on the actual basis of his belief. [That and $2.46 will get you a venti drip from Starbucks if you have your own cup.]
Alan,
Faith has a way of unraveling when you begin to doubt your sacred texts.
Heh. It’s not enough that Salvador wants to claim everything we’ve learned about genetics in the last 60 years is wrong and everything we’ve learned about biology in the last 150 years is wrong. Now we have to hear how everything we’ve learned about geology in the last 250 years is wrong too.
There’s not enough eyerolls and facepalms to adequately cover this amount of willful ignorance.
He is, however, a fully credentialed IDist.
Just noticed this from Sal the Boy Womder in the OP
The pretty discrete changing colors are because it’s a FUCKING ILLUSTRATION you tit.
C’mon, no one can be that stupid, can they?
Apparently.
Because God colored them, Sal, and he’s very good at staying between the lines.
Again, he’s been through all this before, and the facts about sedimentation have been pointed out to him multiple times. Either he has a serious case of selective amnesia or he’s trolling.
Considering that we have to assume he’s posting in good faith, I’ll go with amnesia, but since he doesn’t show any signs that it’s getting better, it’s going to be futile to try to educate him once again. He’ll just forget, and bring up the same “problem” later.
I can hardly wait until Sal tries to explain away the periodic (ie, thousands of years) reversals of the earth’s magnetic field and how it is demonstrated in rock strata all over the world. God playing with a horseshoe magnet?
Gee, I though English was your native language? Did you see the quotes around “buried in”?
In context it’s obvious that fossils are not “buried” in 65 MYo rock by a landslide or whatever 65,000,000 – ~6000 years after the rock formed. They are buried when the rock formed. Fossils found in 65 MYo rock do not counter that claim.
Duh.
None of the references you gave addressed the issue of uranium in situ deposited by groundwater, sometime in mineable concentrations.
If you want to prove you addressed the issue, don’t just claim it; provide the relevant quotes.
I have a theory that I think applies to many but not all YECs.
I must have a get-out -of Hell-free card.
If I interpret the Bible, I might interpret some part wrong.
If I interpret some part wrong, I might not get a get-out-of-Hell free-card.
Therefore, I do not interpret the Bible, and I cannot err in that regard.
Sal’s issues with fossil formation were addressed by Steno 350 years ago. In the age of Galileo. He has some catching up to do.
And Leonardo da Vinci knew that fossils on mountaintops were not formed on mountaintops in the 16th century.
Steno specifically addressed the issue of how fossils became embedded in rock. More than one kind of history.
The following are links to some faded_glory’s comments which I deem to be pointed objections to the YEC model and which must be addressed.
I paraphrase them in the interest of succinctness, but the faded_glorys exact description are linked:
1. older igneous rocks over supposedly younger strata
2. long undeformed sedimentary strata stacked on top of each other going for hundreds of kilometers
3. uniformity of sedimentary strata across oceans
4. how fast continental drift can be reconciled with apparent influence on sedimentary layers
5. reconciling chalk sedimentation rates in short YEC timeframes
6. origin of salt layers hundreds of meters thick in seas and oceans that are on top of fossil bearing strata
7. stratification of fossils into groups rather than mixing
read up on Eustacy and Orogeny.
8. fossils are not dated directly. They are dated by the rocks they are included in, but by surrounding igneous and metamorphic rocks that contain minerals suitable for radiometric dating.
9. look up cratons
10. millions and millions of young fossils managed to find their way many kilometers below the earth’s surface
11. sedimentary rock columns thousands of meters thick full of fossil from top to bottom.
12. microfossils accumulate in seabeds, takes time to form deep layers, not randomly distributed
13.