Question |
Glacial Theory |
Disintegration Theory |
| What
is the significance
of the way cross strata in the sandy drift wraps around embedded
pebbles? |
The
lack of directional
effects is anomalous since the patterns of cross strata are interpreted
as due to fast currents. |
If
the patterns of cross
strata in the drift formed by a non-sedimentary process such as in situ
disintegration there would
be no directional effects such as lee-side tails. |
| The
drift contains an
abundance of rounded pebbles, stones and boulders, that seem to have
been rounded by abrasion during transport in streams. Is that
assumption about their origin correct? |
The
glacial theory
assumes the pebbles and boulders of the drift were transported in
glacial meltwater streams and rounded by abrasion, but the area
required for each rounded pebble and boulder to have been exposed to
the base of the ice and transported for a sufficient distance to become
rounded is lacking; it is unclear how it could have happened. |
The
disintegration
theory says the drift boulders and pebbles formed in place, as
concretionary nodules, during the disintegration process. The idea that
pebbles and boulders became rounded during transport is
unnecessary. |
| The
composition of most
of the pebbles and boulders in the drift reflects local bedrock but
there is also a great variety in their composition. How is that
explained? |
The
glacial explanation
is that pebbles and boulders that are not local to the area have been
brought from distant sources by the ice sheet. But the variety of
pebbles seems greater than the number of possible source areas. |
The
variety of
composition of pebbles and boulders is due to the chemical alteration
of rocks that accompanied the disintegration. This included
crystallization and dehydration, and segregation of the various
combinations of minerals mixed together in concretions as the external
conditions of temperature and pressure rapidly changed. |
| Do conglomerate boulders in the drift indicate multiple ice ages? | The conglomerate boulders in the drift are often interpreted as tillite, or rocks produced by ancient glacial episodes. | The boulders and pebbles of the drift formed in place, already rounded and smooth, as the component minerals separated into nodules. The conglomerate pebbles and boulders in the drift were also formed by concretionary processes. A mass of pebbles was incorporated into a larger concretion, that became a boulder when the surrounding matrix disintegrated. |
| In
some of the cross
stratified
sand and gravels of the drift in southern Ontario the composition of
the boulders and pebbles contrasts with the composition of the sand.
The sand consists of quartz and feldspar, but most of the boulders are
carbonates. How is that explained? |
This
is anomalous in the
glacial theory as the boulders are thought to have been rounded by
abrasion during transport so the finer materials would probably be the
detritus from all the grinding and crushing, so the compositions of
boulders and sand should be similar. |
During
the
disintegration process, the components of a mix of minerals that was
stable at high pressure separated out in response to a lower confining
pressure. Carbonates formed concretions which became boulders when the
matrix around them disintegrated. The matrix may have initially
contained hydrous amorphous silica which crystallized to quartz in
successive layers. The crystallization of amorphous silica is
exothermic so the heat released would have promoted further
crystallization of subjacent layers. The sand produced in this
manner consists mainly of quartz with some feldspar
and minor amounts of other minerals such as garnets and iron oxides. |
| Patterns
of drumlin
orientation in North America seem to correspond to the region of uplift
as indicated by tilted sedimentary cover and the location of exposed
Shield rocks. What is the significance of this? |
No
significance is
indicated in the glacial theory, as the age of the tectonic uplift long
preceded the ice ages. |
The
tectonic uplifts
that caused the tilting of Palaeozoic sediments and exposed the
Canadian Shield caused the catastrophic currents and streamlining of
sediments that resulted in patterns of drumlins. |
| How are stratified drumlins explained? | The stratified drift is attributed to deposition in outwash streams of glacial meltwater. The advancing ice must have passed over these sediments and streamlined the surface. | The streamlining was due to fast currents which shaped the sedimentary rock, and disintegration penetrated the rock after the streamlining occurred. The patterns of stratification in the drift were formed by successive disintegration surfaces, which were fronts of crystallization that penetrated the rock. |
| Drumlins
in some regions
seem to have an orientation that is contrary to the radial pattern
expected by a spreading ice sheet, for example in the Guelph and
Woodstock drumlin felds in southern Ontario, where
the flow was in a northwesterly direction. How is that possible? |
No
explanation available. |
The
currents that caused
the streamlining were generated by uplift of submerged areas towards
the southeast, that spilled waters to the northwest, which caused the
streamlining that produced the drumlins. |
| The
bedrock surface is
irregular beneath drumlins. What is the explanation? |
None
available. |
It
is due to the
variable depth of penetration of the disintegration surface. |
| The orientation of striations on bedrock below the drift and the orientation of streamline features such as drumlins and flutings are used to determine the direction of ice movement in the glacial theory. Do these correspond? | In the glacial theory these should agree since both are attributed to the movement of the ice sheet. | The bedrock striations are attributed to the effects of expansion during the formation of the drift by in situ disintegration. The streamlined features on the drift surface are attributed to fast currents, so these need not correspond. |
| Should the orientations of striations on bedrock beneath the drift and those on exposed surfaces of bedrock correspond? | Since the striations were all made by the movement of the ice sheet, the striations should all correspond. | Striations on exposed bedrock could be due to the transport of boulders by fast currents. Those under the mantle of drift were likely caused by the expansion effects during disintegration. Crossing patterns of striations are common, and these may record effects of both of these mechanisms. |
Do roches moutonnees occur on bedrock surfaces buried beneath the drift? |
Yes,
because the glacial theory says the ice
eroded bedrock before the deposition of the drift, so streamlining of
the bedrock under the drift would be expected. |
No, because if the surface of bedrock was formed by
disintegration, and is buried beneath the drift, it cannot have been
exposed to fast currents. An exception would be if the drift had been
redeposited over a streamlined surface. |
| Eskers
may sometimes
cross over drumlins. Where this occurs, should there be an unconformity
beneath the esker? |
Yes,
because the glacial
theory says drumlins formed when ice was moving, but the esker formed
when the ice was stopped, and deposited its debris in a subglacial
tunnel or crevasse over the drumlin. |
No,
because the eskers
formed where expanding drift layers on either side thrust up a pressure
ridge. The drift strata in the drumlin would be continuous with that in
the esker and form an anticline over it. |
| Which direction should bedrock striations beneath an esker be oriented? | Since eskers are interpreted as ridges of river gravels, and rivers beneath, in or on the ice would probably flow towards the perimeter of the ice sheet, in the direction of ice movement, the general trend of striations would be parallel to the eskers. | Striations would be oriented normal to the trend of the
esker. The expanding drift layers on either side moved towards the
esker which was pushed up as a pressure ridge, that relieved horizontal
stress in the drift. |
| Indicator minerals in the drift were used to locate kimberlite pipes that became diamond mines in Canada. Doesn't that support the glacial theory? | Erosion of bedrock containing kimberlite pipes and the dispersion of the drift by glacial ice is believed to have produced the trains of indicator minerals | At Lac de Gras, samples from the drift in the immediate vicinity of the kimberlite pipes contained hundreds of grains of indicator minerals, while samples from 40 to 50 km in the down current direction contained less than 20 grains. Dispersion of indicator minerals was due to erosion of the drift by fast currents. Patterns of drumlins and other streamlined features indicate the flow directions. |
| How
can large bedrock
rafts of fragile materials such as chalk occur in the drift? |
In
the glacial theory it
is claimed that these have been transported by an ice sheet, but it is
difficult to understand how ice sheets could transport and
deposit huge bedrock slabs without crushing them. |
The
explanation is that they were formed in place, and during the in situ
disintegration that caused
the drift, some sections of bedrock remained intact. |
| Why
are there disintegrated,
rounded sand and clay balls in the drift? |
These
seem rather anomalous in
the Glacial Theory, as disintegrated rocks would not have survived
abrasion during transport. |
They are easily interpreted in an in situ disintegration explanation as there was no transport or abrasion involved. They are concretions or boulders that were disintegrated. |
| What
about prairie
mounds? These are very numerous over vast areas of Western Canada and
parts of the USA. They are elevated plateaux with a rim at the
perimeter, and a depressed center. |
Conventional
explanations invoke depostion of debris from blocks of ice when the ice
melted, but ice sheets generally don't disintegrate into isolated
blocks, they melt at the perimeter. |
They
can be explained as
effects of expansion of the drift during the disintegration process
which formed the drift. Thicker sections of drift expanded laterally
into surrounding regions, pushing up a ridge at the perimeter.
Sediments were deposited as the land slowly emerged from the sea. |