Chapter 18, Problem 1GST

(a)

To determine

The average yearly rate at which the ice in the centre of the glacier advanced.

Answer to Problem 1GST

The average yearly rate at which the ice in the centre of the glacier advanced is $115\text{m}/\text{year}$.

Explanation of Solution

Given info:

Number of years taken for the movement is $8\text{years}$ and the central distance covered centre by the glacier is $920\text{m}$.

Explanation:

The expression for calculating the average yearly rate at which the glacier advanced in the centre,

$\text{The average yearly glacier advancing rate in the centre}\text{=}\frac{\text{Distance covered by the glacier in the centre}}{\text{Time taken for the movement}}$

Substitute $920\text{m}$ for the distance covered by the glacier in the centre and $8\text{years}$ for the time taken for the movement in the above expression to get the average yearly glacier advancing rate.

$\begin{array}{c}\text{The average yearly glacier advancing rate in the centre}\text{=}\frac{920\text{m}}{8\text{years}}\\ =115\text{m}/\text{year}\end{array}$

(b)

To determine

The speed at which the glacier advances per day in the centre.

Answer to Problem 1GST

The speed at which the glacier advances in the centre per day is $0.31\text{m}/\text{day}$.

Explanation of Solution

Given info:

We found from above that the annual rate of movement of the glacier in the centre is $115\text{m}/\text{year}$ and it is also known that a year has $365\text{days}$.

Explanation:

The expression for calculating the speed at which the glacier advances in the centre per day,

$\text{Speed at which the glacier advances per day in the centre =}\frac{\text{Annual rate of glacial movement in the centre}}{\text{Number of days in a year}}$

Substitute $115\text{m}/\text{year}$ for annual rate of glacial movement in the centre and $365\text{days}$ for the number of days in a year in the above expression to get the speed at which the glacier advances in the centre per day.

$\begin{array}{c}\text{Speed at which the glacier advances per day in the centre =}\frac{115\text{m}/\text{year}}{365\text{days}/\text{year}}\\ =0.31\text{m}/\text{day}\end{array}$

(c)

To determine

The average rate at which the ice along the sides of the glacier moved forward.

Answer to Problem 1GST

The average rate at which the ice of the glacier moves forward along the sides is $40\text{m}/\text{year}$.

Explanation of Solution

Given info:

Number of years taken for the movement is $8\text{years}$ and the distance moved along the sides by the glacial ice is $320\text{m}$.

Explanation:

The expression for calculating the average rate at which the glacier advanced along the sides,

$\text{Average glacier advancing rate along sides}\text{=}\frac{\text{Distance covered by the glacial ice along sides}}{\text{Time taken for the movement}}$

Substitute $320\text{m}$ for the distance covered by the glacial ice along the sides and $8\text{years}$ for the time taken for the movement in the above expression to get the average glacier advancing rate along the sides.

$\begin{array}{c}\text{Average glacier advancing rate along sides}\text{=}\frac{320\text{m}}{8\text{ years}}\\ =40\text{m}/\text{year}\end{array}$

(d)

To determine

The reason for the difference in the rate of movement of the glacial ice in the centre and along the sides.

Answer to Problem 1GST

The frictional drags causes the glacial ice to flow at a slower rate along the sides whereas the central part is devoid of friction and can move at a faster rate.

Explanation of Solution

During the movement of glacial ice, the movement occurs both internally and externally. The frictional drag affects the external motion of the ice and it is more along the sides and bottom of the glacier.

The central part of the glacier escapes from the friction. This causes the central part of the glacial ice to advance forward at a faster rate than those along the sides, thus bringing difference in the rate of movement in the centre and along the sides of the glacier.