Transcript Cretaceous Period - Geology12-7

By Dane and Patrick
 Early Cretaceous Epoch - from 145.5 – 127 million
(Neocomian)
years ago.
 Middle Cretaceous Epoch – from 127 – 89 million years
(Gallic)
ago.
 Late Cretaceous Epoch – from 89 – 65 million years
(Senonian)
ago.
 Overall it occurred from 145.5 – 65.5 million years ago
 In between the Tertiary and Jurassic Period.
 The Cretaceous Period was the last period on earth
that had dinosaurs.
 Was named after the chalky rock from Southeastern
England, this was the first sediment studied from the
cretaceous period.
 At this time the breakup of Pangea into serperate
continents was underway.
 The super continent
Pangea was still together
at the start of the
Mesozoic Era.
 It began breaking apart
in the mid Jurassic
Period and was distinctly
separated by the late
Cretaceous Period.
 Volcanic activity assisted
in continental drift.
 Flowering Plants
(angiosperms) flourished
and became very common
 Hardwood began to replace
the Conifers as the
dominant trees of the
forests.
 These new plants provided
fruit and nectar as a new
source of food, causing
great changes in all land
life.
 Dinosaurs continued to
dominate the land but
things had changed from
the Jurassic Period.
Large Sauropods were
rare and armoured
dinosaurs were
becoming common.
 Carnivores were more
common but adapted to
be smaller and more
agile.
 There was a mass
extinction of marine and
land life forms at the end
of the Cretaceous Period.
 Principle casualties were
the dinosaurs and
ammonites.
 No species of land
animal weighing more
than 25kg survived to live
in the Tertiary.
 Nearing the end of the
cretaceous period a 10 km
diameter meteor hit the
earth.
 It caused 75% of the plant
and animal species to
disappear.
 The impact of the meteor
caused it to explode, ash
dust and other debris
spread and actually
blocked out the sun for
almost a year.
 Land covered with forest and surrounded by shallow seas.
 Towards the end of the cretaceous period there was a drop in sea level,
causing land exposure on all continents, more seasonality and greater
extremes between equatorial and polar temperatures.
 Most land mass was at or around sea level until the mid-cretaceous
Sea levels rose, covering 1/3 of the land area
Time of high tectonic activity and volcanic activity
 Many mountain ranges formed at this time such as:
California’s Sierra Nevada
European Alps
 Warm, subtropical climate
No polar ice
 The general breakup of Pangaea into separate continents
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was underway
The separation of Laurasia and Gondwana was complete
Laurasia and Gondwana were 2 supercontinents as a
result of the separation of Pangaea
The Cretaceous period ended 65 million years ago with
the extinction of the dinosaurs, and many prehistoric life
forms
This mass extinction was the second-largest in the
history of the planet
The building of the Rocky Mountains has begun