Week 11

Question 1

Evidence for more massive glaciers catalogued by Jean de Charpentier

Answer 1

GLACIAL ERRATICS

STRIATIONS/GROOVES

ROCHES MOUTONNEES

MORAINES

Question 2

4 ice ages

Answer 2

Günz

Mindel

Riss

Würm

Question 3

Possible reasons for ice ages in 1860s

Answer 3

Pole shift

Earth moving through space

Sun = variable star

Land distribution change

Question 4

James Croll

Answer 4

Astronomical theory of ice ages

1875

Question 5

Milankovich cycles

Answer 5

Eccentricity

• 100,000
• shape

Obliquity

• 41,000
• tilt

Precession

• 21,000
• wobble

Question 6

What affects northern hemisphere timing

Answer 6

Precession

1/2 = N pole points to vega not North Star

Question 7

What controls the timing of the solstice I.e. seasons?

Answer 7

Eccentricity and precession

• n hemisphere winter solstice currently when earth closest to the sun
• I’m 10,500 yrs will be when furthest

Question 8

What kind of glaciation pattern does Croll develop?

Answer 8

Alternating glaciations

When pointing away and furthest

Question 9

Problems with Croll

Answer 9

Actually simultaneous G

Max ice age acc. 80ka B.P. but Niagara Falls erodes 1m/yr = 10-20ka B.P.

Question 10

Milankovich theory

Answer 10

Colder summer T and warmer winter T
=…

Obliquity is key - most land is in the N hemisphere therefore 65’N important

Simultaneous G

Matched geomorphology

Question 11

Problems with milankovich

Answer 11

Geomorphology proven wrong

Orbital variations not enough

Question 12

First ocean sediment core

Answer 12

Swedish deep sea expedition on albatross ship 1947-1949

Question 13

What can foraminifera tell us (and what are they)

Answer 13

= amoboid protists with calcite shell

ISOTOPIC COMPOSITION

WATER T

SALINITY

DEGREE OF DISSOLUTION

DEGREE OF BIOTURBATION

Question 14

What is the 18O signature of forams during G?

Answer 14

High 18O as 16O is locked in continental ice sheets

Question 15

G-IG cycles are controlled by… and modulated by…

Answer 15

Eccentricity

Precession
N.B. Mid-Pleistocene transition ~1ma cycles increased

Question 16

Who popularised the concept of Ice Ages?

Answer 16

Louis Agassiz

Visited geologist Jean de Charpentier in Bex (Swiss Alpine town) 1836

Saw erratics in Neuchatel (far from Alpine glaciers)

1837: theory at Natural History Society meeting
1840: Studies on Glaciers

Question 17

1840 Studies on Glaciers

Answer 17

Ice ages caused extinctions

Ice once covered most of Europe/northern America/northern Asia