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The Time It Rained for 2 Million Years: How Dinosaurs Rose After the Chaos | Prehistoric Documentary — Transcript

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0:01More than 230 million years ago, Pangia
0:04was a vast land mass baking beneath a
0:07dry sky. Then during the Carneium, the
0:10skies began to change. Dark clouds
0:14spread across the superc continent. Rain
0:16began to pour wave after wave. Rivers
0:20burst their banks, forests spread, and
0:23lands that had once been parched slowly
0:25transformed into an unfamiliar world.
0:29This was not an ordinary rainy season.
0:33This chaotic climatic episode may have
0:35lasted nearly 2 million years.
0:38Ancient ecosystems began to collapse.
0:42But in the midst of the crisis, one rare
0:45group of animals began to spread. The
0:47answer begins before the first raindrop
0:50ever fell on Pangia.
0:56About 234 to 232 million years ago
1:00during the late triacic earth entered an
1:02unusual climatic period. Geologists call
1:06it the Carnean pluial episode or CPE.
1:11It was a time of greatly increased
1:12rainfall and a much more active
1:14hydraological cycle on a large scale.
1:18The main phase of the CPE lasted about
1:211.1 to 1.6 million years.
1:25Some studies extend the time frame to
1:28nearly 2 to 2.5 million years.
1:31But the CPE does not mean that Earth
1:34experienced continuous rain for millions
1:36of years.
1:38The climate changed in pulses. Rock
1:41layers show that about four major
1:43rainfall pulses occurred during this
1:45period.
1:47Each pulse brought a wetter interval.
1:49More rain fell. Water flowed more
1:52strongly across vast areas of land.
1:56Then the intensity declined before
1:58another pulse began. This cycle [music]
2:00repeated over a span of time that is
2:02difficult for humans to imagine.
2:05Traces of these changes remain in the
2:07carbon composition of rocks.
2:11After each pulse, researchers found
2:14decreases in the global carbon isotope
2:16ratio.
2:18These changes are known as NCIE with
2:21amplitudes of about 2 to four parts per
2:24thousand.
2:26The number is very small, but in
2:29geology, a change this small can become
2:31an important marker.
2:34When these markers repeatedly appear
2:36alongside rock layers that record
2:38periods of intense rainfall,
2:41they show that the two processes
2:43occurred together. The evidence does not
2:46come from just one [music] place.
2:49It appears in marine sediments and in
2:51sediments deposited on land.
2:54Rock layers formed in different
2:56environments still preserve similar
2:58signals. [music]
3:01This is important. If the evidence
3:03appeared in only one region, the CPE
3:06might have been a local phenomenon.
3:08When similar signals are found across
3:11multiple continents, the story becomes
3:14much broader.
3:16This was a climate change on a global
3:19scale. The timing of the [music] event
3:21provides another clue.
3:24When rock layers are compared with
3:26Earth's astronomical cycles,
3:29researchers find a connection with the
3:31405,000year
3:33orbital eccentricity cycle.
3:36By combining this data with
3:38strategraphy, they can determine the
3:40timing of the climate pulses and [music]
3:42estimate the total duration of the CPE.
3:45Those
3:47numbers take us [music] back to about
3:49234 million years ago.
3:54It was experiencing repeated periods of
3:56intense rainfall over more than a
3:58million years.
4:01Today, those rains have been gone for an
4:04unimaginably long time.
4:07No triacic river still flows across the
4:10land. [music] No ancient sky remains for
4:12us to watch those storms. But the rocks
4:15are still there.
4:17Within them are traces of water, carbon,
4:20[music]
4:20and time. When these traces are found
4:23both in marine and terrestrial
4:24environments across multiple continents,
4:27they tell the same story.
4:32About 234 million years ago, Earth's
4:35hydraological cycle changed on a global
4:37[music] scale.
4:40The CPE is not recognized only through
4:43rock layers that record rainfall.
4:47The climate changes [music] of that time
4:49also left other signals in the
4:51geological record.
4:54Those next clues will show us how this
4:56extraordinary period unfolded.
5:01Before the CPE, nearly all of Earth's
5:04major land masses were still joined
5:06together as pangia,
5:08a gigantic superc continent stretched
5:10across many latitudes. The farther
5:13inland you traveled, the harsher the
5:15climate became.
5:17Moisture from the oceans struggled to
5:19reach deep into the center of pangia.
5:24Heat lasted for long periods. Rain was
5:27scarce. Dry seasons came often.
5:31Across many inland regions, aridity
5:34became a familiar condition. The great
5:36mountain ranges running through pangia
5:39made the situation even more severe.
5:41Moist air blowing in from the sea
5:43encountered the mountains.
5:47Extensive layers of red sediment appear
5:49across the landscape. Evaporide layers
5:52are also found.
5:54They formed when water evaporated and
5:57left behind salt and minerals.
6:00Many rock layers also show clear signs
6:03of distinct dry seasons. Together they
6:05create a consistent picture.
6:09Before the [music] CPE, pangia was a hot
6:12and dry world where water was difficult
6:14to find deep within the interior.
6:18On that dry land, species capable of
6:20surviving with little water had a major
6:22advantage.
6:25Pseudosuchio was one of the most
6:26prominent groups. These were ancient
6:29reptiles closely related to modern
6:31crocodiles.
6:33Many species were large and common in
6:35terrestrial ecosystems. Living alongside
6:38them were synapsids, another ancient
6:40branch of animals that played an
6:42important role across pangia. [music]
6:44And what about the dinosaurs?
6:47They had already appeared, [music] but
6:49they were still very rare. The earliest
6:52species were generally small. Their
6:56fossils and footprints made up only a
6:58very small portion of the record in many
7:00early rock layers.
7:04In many places, the proportion was below
7:075 to 10%. [music]
7:08Some layers contain almost no trace of
7:11dinosaurs at all.
7:13At that time, [music] they were not yet
7:15a dominant group across the dry lands of
7:17pangia.
7:19So just before [music] the CPE, Pangia
7:22looked very different from the world of
7:24dinosaurs we usually imagine,
7:27a hot dry superc continent, vast deserts
7:30[music]
7:31deep within the interior,
7:34mountain ranges creating broad rain
7:36shadow regions, [music] red sediments
7:38and layers of salt preserved in the
7:40rocks
7:42across the land. Pseudosia and synapsids
7:45[music] still held the advantage.
7:48that stability would not last forever.
7:51The climate [music] began to change.
7:53More water entered the climate system.
7:56And when the heavy rains of the CPE
7:58arrived, Pangia's dry [music] world
8:00began to enter a very different phase.
8:04About 234 million years ago during the
8:08Carneian, a massive volcanic region was
8:11highly active in the western part of
8:12Panthalasa. [music]
8:15Today, remnants of this region are found
8:17in Alaska and British Columbia.
8:21At that time, it still lay beneath the
8:23Panthalasa Ocean.
8:27Geologists call it the Reangelia Large
8:29ignous province [music] or Reangelia
8:32lip.
8:34Reangelia was not a single volcano.
8:37[music] It was a vast region of magma.
8:40During each eruption, magma from deep
8:43within Earth rose onto the ocean floor.
8:47These eruptions occurred in pulses. Each
8:50pulse may have lasted several
8:52hundred,000 [music] years.
8:55The amount of carbon Reangelia released
8:57into the Earth system was enormous.
9:01Some models estimate that Reangelia
9:03alone released about 5 [music] * 10 18th
9:07power g of carbon.
9:10But that amount was still not enough to
9:12explain the full scale of the carbon
9:14changes recorded [music] during the CPE.
9:18This suggests that the volcanoes may
9:20have been the main trigger, but they
9:22were not the only source of carbon.
9:26As CO2 levels rose, other carbon sources
9:29may have begun to respond.
9:33One of them was methane hydrates,
9:35icelike structures that can trap methane
9:37beneath the seafloor. [music]
9:40When environmental conditions change,
9:42methane can be released. Organic carbon
9:45may also have contributed [music] to the
9:47process.
9:49These additional carbon sources could
9:51have made the initial impact from
9:53Reangelia much stronger.
9:56Carneian rock layers also preserve more
9:59direct signs of volcanic activity.
10:02When HG levels rise in rock layers from
10:05the same period as the CPE, it becomes
10:08evidence that strong volcanic activity
10:10was occurring at that time.
10:14Another signal found in the sediments is
10:16nonraiogenic osmium.
10:20When these data are placed alongside the
10:22carbon signals, they all point to a
10:25period of intense geological activity.
10:29There is not just one trace. Multiple
10:32traces are preserved within the same
10:34layers of rock.
10:36More importantly, the eruptions of
10:38Reangilia did not occur randomly.
10:40[music] They happened in distinct
10:42pulses.
10:44Each pulse lasted several hundred,000
10:47years. [music]
10:48These pulses occurred at times that
10:49closely coincide with separate NCIs in
10:52the geological record.
10:56One episode of volcanic activity
10:58occurred alongside a carbon shift. Then
11:01another episode appeared with a new
11:02signal. The pattern repeated several
11:05times.
11:08This close timing has made Reangelia a
11:11leading candidate for the main trigger
11:12of the CPE.
11:15The volcano's released CO2 into the
11:18system. Methane hydrates and organic
11:20carbon may then have added more carbon.
11:24Sedimentary layers recorded Hg, mercury
11:27isotopes, and [music] osmium.
11:30The volcanic pulses also appeared
11:32[music] close in time to individual NCI
11:36and traces of each episode remained
11:38locked in the rocks for more than 230
11:40million years.
11:43But the volcanic [music] activity was
11:45only the beginning of the story. What
11:47happened after CO2 levels rose
11:50helps explain why the climate changes
11:52during [music] the CPE became so
11:54powerful and lasted for so long.
11:59After the eruptions of Reangelia, CO2
12:01began to rise sharply in the atmosphere.
12:04More heat was trapped. Earth warmed.
12:08Studies [music] produce different
12:09estimates, but the global increase may
12:11have been around 3 to 8° C.
12:15During periods of intense warming, many
12:17studies record around 4 to 7° C or
12:20higher.
12:23As temperatures rose, the oceans [music]
12:25began to respond. Warmer sea water
12:27evaporated more quickly.
12:31More water vapor entered the atmosphere.
12:33Monsoons also became stronger. Air
12:36carried more moisture from the oceans
12:38onto the land. When moisture levels
12:40became high enough, rainfall became more
12:43intense. Runoff across the land
12:45increased as well.
12:50But the rain did not fall evenly across
12:52pangia. Climate models show clear
12:55differences between [music] regions.
12:58Some low latitude areas in eastern
13:01pangia may have received much more
13:03rainfall.
13:05Regions near the poles also tended to
13:07become wetter. Meanwhile, the interior
13:10of pangia may have become drier.
13:14The farther from the ocean, the harder
13:16it was for moisture to penetrate [music]
13:18deep into the center of the superc
13:19continent.
13:22So [music] the CPE did not turn all of
13:24Pangia into a wet landscape.
13:28Some places received much more rain.
13:30Others became drier.
13:34Stronger monsoons brought more water
13:36into the system, but that water was
13:38distributed differently from one region
13:41to another.
13:43This difference helps explain why
13:45paleocclimate models show opposite
13:47responses in different areas during the
13:49same period.
13:51Even more striking was the speed of the
13:53change.
13:56Some ancient lakes in China preserve
13:58sediment layers with exceptionally high
14:01resolution.
14:04Data from these lakes suggest that part
14:06of the climate shift may have occurred
14:08in only about 15.8,000 years.
14:12In the history of Earth, that is an
14:15extremely short period of time.
14:20During that time, rising temperatures
14:22may have fed back into the carbon cycle.
14:25Some carbon sources at Earth's surface
14:27may have [music] released additional
14:29carbon. More carbon made the climate
14:31warmer.
14:34Higher temperatures continued to
14:36increase evaporation from the oceans.
14:38Water vapor increased.
14:42Rainfall changed. Runoff changed. These
14:46processes followed one another and may
14:48have accelerated the pace of climate
14:50change.
14:52So what happened during the CPE was not
14:55simply a rise in temperature.
14:58Rising CO2 warmed earth. Warmer oceans
15:01increased evaporation. Monsoons became
15:04stronger.
15:07Rainfall increased in some regions. The
15:10deep interior of pangia could remain dry
15:12or even become drier than before.
15:16In a very short period compared with
15:18geological history, temperature and the
15:21water cycle changed together
15:25from a hot dry earth. The climate system
15:28began shifting into a new state.
15:33And this major change in water across
15:35the land left clear traces in the
15:38sedimentary layers formed during the
15:40CPE.
15:45More than 230 million years ago, Earth
15:48entered a period when water left traces
15:51throughout the rocks.
15:53When we say the CPE lasted nearly 2
15:56million years, it does not mean that it
15:58rained every single day.
16:01Rainfall and runoff increased through
16:03multiple episodes.
16:06Water flowed from the land into [music]
16:08rivers, carrying more and more material
16:10toward the seas.
16:13At the same time, rocks on the
16:15continents were broken down by water
16:17more rapidly.
16:20The first [music] evidence appears in
16:21the degree of weathering recorded in the
16:23rocks.
16:25Chemical index of alteration or CIA
16:28values increased clearly in many
16:30records.
16:32Kolinid also became more abundant. These
16:35two signals show that water had a strong
16:38effect on rocks during the CPE.
16:41There was more rain, water penetrated
16:43[music]
16:44deeper, rocks were altered more quickly
16:48and the amount of material carried away
16:50from the continents also [music]
16:51increased.
16:55The flowing water then carried large
16:57amounts of sediment into the [music] tey
16:59seas.
17:01Before the CPE, many basins there
17:03contained carbonate platforms.
17:06These new sediments gradually covered
17:09the carbonate platforms.
17:12In many basins, they replaced the
17:14earlier carbonate deposits. This change
17:17is known as the Reinrain turnover.
17:20Another clue comes from fragments of
17:23ancient amber. During the CPE, amber
17:27appeared across a wide area and was
17:29especially abundant in the Dolommites in
17:31what is now Italy.
17:37Drops of tree resin were buried and
17:39became amber. Some specimens still
17:41contain [music] ancient microorganisms
17:43and arthropods.
17:46They were trapped inside the resin
17:47[music] like tiny images of a world that
17:50disappeared long ago.
17:53Ancient soils tell a similar story. Some
17:56paleosols carry signs of wet
17:58environments.
18:01Histic and spottic forms appeared or
18:03increased in some regions. Hydrofitic
18:06plants also became more common.
18:09These signs show that water was not only
18:12more abundant in rivers and across the
18:14land surface.
18:16It also had a lasting effect on soils
18:19and vegetation. In some places, water
18:22penetrated deep into the ground.
18:25Signs of carst and caves have been found
18:28in certain rock layers. Rainwater
18:30entered cracks.
18:33It dissolved carbonate rock and widened
18:35spaces beneath the ground.
18:39This process left structures that can
18:41still be recognized in ancient rocks
18:43today.
18:45Eruptions released sulfur gases into the
18:47atmosphere. When they mixed with water,
18:50these compounds could produce acid
18:51[music] rain.
18:54Acidic rainfall acted strongly on rocks,
18:57especially limestone and other carbonate
18:59rocks.
19:01As a result, increased rainfall and
19:03volcanic activity may have worked
19:05together to accelerate weathering.
19:09Each sign appeared in a different place.
19:11But when they are placed together, they
19:13become remarkably consistent.
19:17CIA increased, kale lenite increased.
19:21Saliclastic sediments poured into the
19:23teus.
19:25Carbonate platforms were replaced in
19:27many basins. Amber became more
19:29widespread. Wet soils and hydrofitic
19:32plants increased.
19:35Carst and caves formed in some places.
19:37Acid rain [music] continued to speed up
19:39the weathering of rocks.
19:42That is why the nearly 2 million-year
19:44rain should not be imagined as an
19:46endless storm.
19:48It was [music] a period when water
19:50became more active across Earth through
19:52multiple episodes and each episode left
19:54its mark in the rocks. Those traces
19:59connect the land to the sea from ancient
20:01soils to drops of amber,
20:04forming geological evidence for one of
20:06the most notable wet periods of the
20:08triacic.
20:10From these changes on land, the fossil
20:13record began to reveal another
20:15transformation that was just as
20:16important.
20:19During the CPE, life began to disappear
20:22in both the seas and on land.
20:26Meta analyses show that about 33% of
20:29marine genera disappeared.
20:32This does not mean that every group
20:34suffered the same losses. Some groups
20:36nearly collapsed while others survived,
20:41but the scale of the losses was large
20:43enough to clearly change triacic marine
20:45communities.
20:48Connidants were among the hardest hit
20:50groups. In some regions, [music]
20:52about 70% of genera disappeared.
20:56These small organisms had once been
20:58widespread throughout the ancient seas.
21:02Then their traces became increasingly
21:04rare in the rock layers.
21:08A group that had once been common began
21:10disappearing from many regions. [music]
21:12Ammonoids were also affected by the
21:14upheaval.
21:16The trackeri group was especially hard
21:19hit. Many lineages declined sharply or
21:22disappeared.
21:25Kryoids and briazoans also suffered
21:27major losses.
21:31Many marine organisms that had [music]
21:33lived in shallow seas faced unfavorable
21:35conditions. At the same time,
21:38the decline was no longer limited to a
21:41single group. Carbonate platforms also
21:44began to shrink.
21:47These were large carbonate [music]
21:48systems that had once developed in
21:50shallow seas.
21:54As more fresh water flowed from the land
21:56into the [music] oceans, it carried
21:58large amounts of nutrients with it.
22:01The seawater [music] changed as a
22:03result. Organisms grew more rapidly in
22:06some areas.
22:07When the increased organic matter died
22:10and decomposed, oxygen in the water was
22:12consumed.
22:14Low oxygen zones [music] or enoxia began
22:17to appear or expand.
22:21At the same time, [music] the chemistry
22:23of seawater also changed. Acidification
22:26made conditions [music] more difficult
22:27for organisms that needed carbonate to
22:29build shells or skeletons.
22:33Carbonate platforms therefore faced
22:35another pressure. Less oxygen, changing
22:38chemistry.
22:41On land, another group of herbivores
22:43also began to disappear. These were
22:46wrenchosaurs.
22:49Before the CPE, they accounted for about
22:5240 to 60% of the animals in some
22:54communities.
22:57But in Argentina and Brazil, their
22:59traces later almost disappeared.
23:02Desinodants also took a heavy blow.
23:06Their abundance and diversity declined
23:08significantly. However, they did not
23:10disappear immediately.
23:13Some lineages survive longer and are
23:15recorded as late as about 219 million
23:18years ago.
23:21Their decline therefore unfolded over
23:23several stages rather than ending at one
23:26single moment.
23:29In the seas, about 1/3 of marine genera
23:32disappeared.
23:34On land, herbiviverous groups that had
23:36once made up a large share of
23:38communities also declined.
23:41Connodants lost up to about 70% of
23:43[music] their genera in some regions.
23:47Ammonoids, kryinoids, and brioans all
23:50suffered losses. Carbonate platforms
23:52contracted. [music]
23:55Anoxia and acidification developed in
23:57marine environments. Rinosaurs [music]
23:59nearly collapsed in parts of South
24:01America.
24:03Dicinodons also declined sharply. This
24:06is why the CPE is regarded as a major
24:09background extinction event.
24:12It did not wipe out all life, but it
24:15removed many groups that had once held
24:17important positions in ecosystems.
24:20Afterward, marine and terrestrial
24:23communities were no longer the same.
24:26Groups that had once been common became
24:28rare or disappeared. The survivors
24:31entered a world with fewer competitors.
24:36That change created a large opening in
24:38triacic ecosystems. As many herbivores
24:41and marine organisms declined, [music]
24:44important ecological positions were left
24:47vacant. Other groups began moving into
24:50those positions.
24:53Among the survivors was a group that was
24:55still relatively small at the time,
24:59but would go on to change the history of
25:01life on Earth, the dinosaurs.
25:07About 234 million years ago, dinosaurs
25:11were still very rare across pangia.
25:15They made up only a small fraction of
25:17tetropod communities.
25:20Footprints tell a similar story. In many
25:23early rock layers, dinosaur tracks are
25:25almost absent.
25:28At that time, they were still a minor
25:30group among the reptiles that dominated
25:32the land.
25:34The climate began to change during the
25:36CPE. Over the 3 to 4 million years
25:39surrounding the event,
25:42evidence of dinosaurs increased rapidly.
25:45One of the clearest records comes from
25:46the Dolommites in Italy.
25:49In the Julian layers, dinosaur tracks
25:52are almost absent, but by the early
25:54Talian, they accounted for about 40% of
25:57the recorded tetropod tracks. [music] In
26:00younger layers, that figure rose above
26:0290%.
26:05The change is easy to see in the rocks.
26:07At first, a dinosaur [music] footprint
26:09was something rare.
26:13Among them were the earliest
26:14sorapottomorphs and early therapods.
26:17Herrerasaurus was one of the notable
26:19names.
26:21Eoraptor also appeared during this early
26:23stage. They were [music] not yet the
26:25giant dinosaurs of tens of millions of
26:28years later.
26:30At the same time, the older herbivores
26:33were declining. Renosaurs had once made
26:36up as much as 40 to 60% of some
26:38communities.
26:41Dicinodons were also widespread. But
26:44after the CPE, both groups declined
26:46sharply.
26:49A large part of the herbivores that had
26:51once fed across pangia either [music]
26:53disappeared or became much less common.
26:57A gap opened on the land. Food was still
27:00available, but the groups that had once
27:02used those resources were no longer as
27:05numerous.
27:07The climate also became wetter in many
27:09regions. Vegetation changed. Areas with
27:13more water expanded.
27:16In this new world, dinosaurs had more
27:18room to grow and spread.
27:22Their respiratory system may have helped
27:24them adapt to these conditions. [music]
27:26Many dinosaurs had air sack systems
27:28connected to their lungs.
27:31This form of breathing allowed air to
27:33move efficiently through the body.
27:36When temperature and humidity changed
27:38sharply, [music] that feature may have
27:40given them an advantage.
27:43This was not a change that happened
27:45overnight. It unfolded over millions of
27:48years.
27:50But in Earth's history, a few million
27:52years is a short span of time.
27:56Dinosaurs went from being a rare group
27:58to becoming the animals leaving dense
28:01trails of footprints across lands that
28:03had once [music] belonged to other
28:04species.
28:06The CPE changed the environment. Older
28:09herbivores declined. Wet regions
28:12expanded.
28:14Vegetation changed. At the same time,
28:17dinosaur lineages began to diversify.
28:22These conditions [music] came together
28:23and opened the way for their expansion.
28:26From the few footprints in the Julian
28:28layers, a new story began.
28:32Dinosaurs were no longer standing at the
28:34edge of the ecosystem. They were moving
28:36toward the center.
28:39As that space opened, dinosaurs were not
28:42the only ones to benefit.
28:45Many other reptiles, plants, and animals
28:48also began to thrive in [music] the new
28:49world after the CPE.
28:53After the CPE, the living world across
28:56pangia began to change. Older groups had
28:59declined.
29:01The survivors began filling new
29:03ecological spaces. The first changes
29:06could be seen in plants.
29:09Conifer families related to modern
29:11groups began diversifying rapidly.
29:14Benadet tales also expanded
29:18in regions with more water.
29:19Moisture-loving plants became
29:21increasingly common.
29:24As vegetation changed, the animals
29:26living on land changed as well.
29:28Crocodiles began to appear or diversify
29:32early.
29:34These were ancient relatives of
29:35crocodiles. Some lived on land and
29:38looked very different from crocodiles
29:40today.
29:42Turtles also appeared in triacic
29:44communities. At the same time, some
29:47lineages distantly related to lizards
29:50and mammals began to diversify.
29:54Adosaurs also increased. They were
29:56herbivorous reptiles with rows of bony
29:59plates running along their bodies.
30:03As the land environment changed,
30:05Adosaurs expanded in areas with suitable
30:08plant resources.
30:10They became one of the notable
30:12herbivorous reptile groups of the late
30:14triacic.
30:16Phytosaurs began to thrive. They had
30:18long bodies and long snouts, making them
30:21look very much like crocodiles.
30:25But they were not crocodiles. They were
30:27semi-aquatic reptiles that lived in
30:29ancient freshwater systems.
30:33On land, a new picture was taking shape.
30:36Conifers and benitalies became more
30:38diverse. Moisture loving plants
30:40increased.
30:43Crocodiles and turtles appeared or
30:45expanded. Adosaurs increased. Phytosaurs
30:49flourished in rivers and lakes.
30:52Many groups were expanding in a world
30:54that had just gone through major
30:56environmental change.
30:59The oceans were changing as well.
31:02Scleractinian corals began building
31:04coral reefs.
31:07These tiny organisms could [music]
31:09create large carbonate structures
31:11underwater.
31:13The new reefs provided habitats for many
31:16other marine organisms.
31:19This marked [music] an important step in
31:21the history of coral reefs. Calcarious
31:24nanop fossils also became more common.
31:27They were extremely small and could only
31:30be seen under a microscope.
31:34But the carbonate material they produced
31:36could become preserved in marine
31:38sediments.
31:40Their increase shows that ocean
31:42chemistry was [music] changing.
31:43Carbonate production in the open ocean
31:46was also becoming more important.
31:47[music]
31:49These changes took place on both land
31:51and sea.
31:55Conifers and benites expanded. Moisture
31:58loving plants increased.
32:01Reptile groups such as crocodiles,
32:04turtles, and adosaurs developed.
32:08Phytosaurs occupied rivers and lakes. In
32:11the oceans, scleractinium corals began
32:14building reefs.
32:17The CPE therefore did more than make
32:19some groups [music] disappear. It also
32:22opened opportunities for many others.
32:25Some groups had already existed but
32:27began diversifying rapidly. Some groups
32:30became more clearly represented in the
32:32fossil record.
32:34Many of these lineages would continue
32:36for tens of millions of years afterward.
32:43Looking back from the present, part of
32:45the natural world we recognize [music]
32:47today began taking shape during this
32:49period.
32:51Conifer families still live on Earth.
32:53Crocodiles and turtles still survive.
32:57Hard corals still build [music] reefs
32:59beneath the sea.
33:04More than 230 million years ago, these
33:07groups were only beginning to enter a
33:09new period of expansion.
33:12The CPE had changed the environment
33:14around them.
33:18As the eruptions of Reangelia weakened,
33:21the amount of carbon released into the
33:23atmosphere also decreased.
33:26The new source of heat was no longer as
33:28strong as before.
33:31Carbon began to be buried in layers of
33:33sediment. Weathering of rocks on the
33:35continents continue to remove CO2 from
33:37the atmosphere. As a result,
33:39temperatures gradually fell.
33:43Rainfall also began to decrease. The
33:45water cycle was no longer as intense as
33:47it had been during the CPE.
33:51Regions that had once received heavy
33:53rainfall gradually became drier. Pangia
33:56returned to the hot, dry climate that
33:57had been common before.
34:00The rainy period that had lasted for
34:02millions of years had come to an end.
34:07But life did not return to its former
34:09state. Groups that had once been common
34:11before the CPE had declined.
34:14Other groups had increased. Dinosaurs
34:17were among them. They continued to
34:19expand even as the climate began to
34:21become drier.
34:23Before the CPE, dinosaurs were only a
34:26minor group.
34:31After the CPE, their footprints and
34:33fossils became increasingly common.
34:36Serishian lineages continued to
34:37diversify.
34:40Therapods and sorapotamorphs expanded
34:42into many different environments.
34:45From a rare group, dinosaurs gradually
34:48became a major force on land. That
34:51change did not end with the CPE.
34:55Dinosaurs continued to hold a dominant
34:57position for more than 160 million years
35:01afterward.
35:03They appeared across many regions of the
35:05world. [music] Some lineages became
35:07large predators.
35:09Others evolved into enormous herbivores.
35:12Many smaller lineages also lived
35:14alongside them.
35:17Plants also left a lasting mark.
35:20>> [music]
35:20>> Conifer groups continued to develop and
35:22became important components of many
35:24forests.
35:26Other plant groups also became more
35:29clearly established. At the same time,
35:31many vertebrate lineages continued to
35:34develop in the new ecosystems after the
35:36CPE.
35:38Beneath the [music] sea, the changes did
35:40not disappear when rainfall decreased.
35:44Carbonate ecosystems continued to be
35:47rebuilt.
35:49corals continued to develop.
35:52Carbonate producing organisms played an
35:54increasingly important role in marine
35:56environments.
35:58The changes that began during the CPE
36:01continued to leave their marks in layers
36:03of rock.
36:05The story of the CPE therefore began
36:07with volcanoes and ended with a
36:10different world.
36:12Reangelia was highly active. Carbon
36:14increased, temperatures increased,
36:16rainfall increased. Then the volcanoes
36:19weakened, carbon was buried, weathering
36:22removed CO2 from the atmosphere,
36:24temperatures fell, pangia became drier
36:27again.
36:29But the ecosystems had changed. That is
36:31the most important point of this period.
36:35The climate could gradually return to a
36:37hot, dry state. But the groups of
36:40organisms that had disappeared did not
36:42return. The groups that had expanded
36:46continued to thrive. Dinosaurs continued
36:49to advance.
36:52Conifers continued to survive. Many
36:55vertebrate lineages began to take
36:57clearer shape.
37:00The CPE reveals a very clear sequence of
37:03events in Earth's history. Volcanic
37:06activity released carbon into the
37:07atmosphere.
37:09The climate changed. The water cycle
37:12changed. Ecosystems were affected.
37:17As volcanic activity declined, the
37:19climate gradually stabilized, but life
37:22had already moved in a new direction.
37:26More than 230 million years later, those
37:29traces still remain in the rocks.
37:33layers of sediment record changes in the
37:35climate. Fossils show which groups
37:37disappeared [music] and which ones
37:39expanded.
37:40Dinosaur footprints show how a group
37:43that was once very rare became a
37:45dominant force.
37:48The CPE did not last forever. The final
37:52reigns eventually ended, but what they
37:54left behind lasted far longer.
37:58Dinosaurs entered an age of dominance.
38:00[music]
38:01Many groups of plants and vertebrates
38:03continued to develop
38:06beneath the seas. New ecosystems formed
38:09and expanded.
38:12One chapter of Earth's climate had
38:14ended, but a new chapter in the history
38:16of life had just begun.
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40:50explore ancient Earth, uncover forgotten
40:53knowledge, and investigate the mysteries
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