Modern Monuments (L26)

Question 1

what are the 3 main stages recognized in the development of Stonehenge?

Answer 1

the first version built at approx 3000 BCE (circular ditch with small pits called Aubrey Holes)

2500 BCE - blue stones instralled at the centre shape of a horseshoe

2300 BCE - 30 sarsen stones (slabs of hard -silica semented sandstone) vertically imbedded in the ground

Question 2

What rock is most of the bluestones made out of?

Answer 2

intrusive igneous rocks called diabase

Question 3

What problem is there when speculating that the bluestones were quarried in Wales and dragged to Stonhenge?

Answer 3

there is a 500 year time gap

Question 4

What is a possible alternative to the Wales quarry hypothesis?

Answer 4

possible that during the last Ice Age, ice sheets could have transported diabase slabs from Wales to English coasts

Question 5

What is the trillithon?

Answer 5

three-stone structure that formed through sarsen stones formed in a horseshoe arrangement and capped by horizontal lintels

Question 6

What is the Slaughter Stone?

Answer 6

it is a flat stone in Stonehenge that has little pits in the surface with a rusty brown color

name comes from people believing that it was stones where sacrifices were carried out and thought that the hematite rust was actually blood of the victims

Question 7

What is an interpretation of what the purpose of Stonhenge was?

Answer 7

One popular interpretation is that Stonehenge functioned as an ancient observatory
and the arrangements of standing stones in the final version of Stonehenge marks the positions of the moon and sun during diff times of the year

Question 8

Where is Mount Rushmore made?

Answer 8

in the Black Hills - represent an upwarded structure underlain by very old mica schists dating back to the Proterozoic

Question 9

How was Black Hills created?

Answer 9

about 60-70 million years ago, the batholith was uplifted and the overlying sedimentary rocks warped

erosion then removed sedimentary rocks in the central part, leaving slanted strata

Question 10

What are the 3 rock types observed in the Black Hills?

Answer 10

Protoerozoic scihsts (oldest rocks)
Paleozoic/Mesozoic sedimentary rocks
overlain by flat-lying Cenozoic sedimentary rocks in turn overlies the titled strata

Question 11

Why was the original site “The Needles” deemed unsuitable for carving?

Answer 11

due to the severe jointing

Question 12

How was the carvings made on Mt Rushmore?

Answer 12

excess granite had to be removed by dynamite, creating the head shapes

then finer details were carved through honeycombing

then workers used a pneumatic drill with a special bit to smooth out the honeycomb marks

Question 13

What is honeycombing?

Answer 13

the method involved the drilling of holes to specific depths into the vertical cliff surface and removing intervening rock between the holes with hammers and chisels

Question 14

What is a reason CN Tower is a monument of modern significance?

Answer 14

CN Tower is made largely of concrete which is the modern material of choice for construction in today’s world

Question 15

CN Tower is ______

Answer 15

one of the world’s tallest freestanding structures

Question 16

What were the 2 reasons why CN Tower was originally built?

Answer 16

Toronto had a huge construction boom of creating large skyscrapers and this caused communications problems (bad signal) so put transmitters and receivers very high above the ground to resolve this

also the CN company wanted to demonstrate the strength of Canadian industry

Question 17

How was the concrete shaft created?

Answer 17

slip forming - involves pouring concrete into a massive mould or “slipform” and jacking the mould upward in steps

Question 18

Why is it good that the CN Tower is elastic and sways a bit?

Answer 18

b/c if the tower was completetly still, the top would be in danger of snapping off

Question 19

What is Concrete?

Answer 19

a mixture of cement, sand, rock, water, and small amounts of additives

Question 20

How are concrete and cement different?

Answer 20

concrete CONTAINS cement as a binding ingredient

Question 21

What is Cement?

Answer 21

the abbreviation of the more correct name, “Portland Cement” and is fine grey powder

Question 22

what are 2 raw materials used for cement production?

Answer 22

calcite and silica

Question 23

How is cement made?

Answer 23

1. the raw materials are measured into desired quantities and crushed in multiple stages into a fine powder
2. the powder is then fed into a preheating tower and cooked (preheating stage)
3. the pre-heated material is then fed through a rotary kiln that heats the mixture further
4. then the calcium reacts with the silica and a clumpy substance called clinker comes out
5. the clinker is cooled, mixed w a small amount of gypsum and milled into a fine powder

this fine powder is cement

Question 24

What happens when you add water to cement?

Answer 24

the water reacts with the calcium silicate to produce needle-like crystals of calcium silicate hydrate and calcium hydroxide

Question 25

How does cements hardening work?

Answer 25

the calcium silicate hydrate crystals form an interlocking network, and this is what gives concrete its strength when dry

Question 26

What are other mterials that need to be added to create concrete?

Answer 26

aggregate meterial such as sand and gravel adds bulk to the concrete and workes as a filler

Question 27

Why is there no shortages of ingredients for cement production in Ontario?

Answer 27

Ontario has lots of limestone and sandstone as large deposits of sand and gravel were deposited when these continental glaciers of the last ice age melted

Question 28

What are eskers?

Answer 28

snake-like landforms left behind from accumulations resulting from retreated ice sheets and well-sorted sand and gravel were deposited from the subglacial rivers

Question 29

Ultimately, what are the materials that made the CN Tower?

Answer 29

limestone, sandstone, shale from the Paleozoic bedrock of Ontario deposited plus the aggreagate that was deposited from the last ice age