Form 4 Term II

Question 1

What is a watershed?

Answer 1

A boundary of the drainage basin. It is made up of highlands or mountains. It separates two drainage basins

Question 2

What is a source?

Answer 2

The start of a river eg. Mountain, spring or ice

Question 3

What is a mouth (estuary)?

Answer 3

When a. river ends into the sea

Question 4

What is a confluence?

Answer 4

When a tributary meets a main river

Question 5

What is a dendritic drainage?

Answer 5

A dendritic drainage is where the drainage pattern looks like a tree. The main river is like the ‘trunk’, the larger tributaries are the main branches and the smaller tributaries form a pattern like little branches and twigs coming from the larger tributaries n trunk.

Question 6

What is a trellis drainage?

Answer 6

The trellis drainage is where the pattern has an appearance of a rectangular grid. Rivers and their tributes flow almost perpendicular to each other, with confluence at an angle close to 90°.

Question 7

What is a radial drainage?

Answer 7

This is when rivers radiate from a central point, like the spokes of a wheel from a tire. Rivers on volcanic cones often develop radial drainage patterns.

Question 8

What is rock type?

Answer 8

Different river patterns will flow based on the type of rock it flows over. Eg. Hard resistant rocks such as igneous rocks will have few rivers. Soft rocks such as sedimentary rocks will have more rivers.

Question 9

What is Geology?

Answer 9

The structure of rocks. The presence of joints, pores and the relief of height of the rocks structure. This will influence the types of drainage patterns.

Question 10

What are the processes of a river?

Answer 10

The river’s energy - The power of the river
The volume - The amount of water in a river
The velocity - The speed of the river
Gradient - Height of the river eg. Mountain
Discharge - The amount of water passing at a particular point and time in a river
Density - The number of streams, tributaries and river in a drainage basin.

Question 11

What is the rivers energy mainly used for?

Answer 11

Overcome friction

Question 12

What is hydraulic Action?

Answer 12

This occurs when there are cracks or joints on the bed and banks of the river. Air enters the cracks and joints. When the river is filled with water, the water enters the cracks and joints. The water compresses the air, causing the cracks n joints to widen and deepen causing the rocks to break apart.

Question 13

What is corrasion/Abrasion?

Answer 13

This is the wearing away of the bed and banks of the river by the land carried in the water. The large rock boulders, and pebbles hit against the bed and banks causing pieces of rocks to loosen and break off aka the sand paper effect.

Question 14

What is attrition?

Answer 14

This occurs when the material or river land such as huge angular rocks hit and collide with each other in the swirling, turbulent water. As they hit, they break up into smaller pieces, becoming smooth and rounded.

Question 15

What us corrosion/solution?

Answer 15

The process of carbonation/solution causes river rocks to dissolve and wash away in solution. When rain falls, it mixes with carbon dioxide in the air. This forms a weak carbonic Acid. This water flows in the river dissolving the rocks that are made up of chalk and limestone. The calcium carbonate in the limestone is dissolving and washed away as a soultion, calcium bicarbonate.

H2O + Co2 = H2 Co3 + CaCo3 = Caco6

Question 16

How is gradient calculated?

Answer 16

Vertical Distance = VD = Rise
Horizontal Distance= HD = Run

Question 17

What are the 3 courses of a river?

Answer 17

Upper course, middle course and Lower course

Question 18

What is the upper course?

Answer 18

The river has a V - shaped valley because of deep vertical erosion of the bed of the river.

Question 19

What is the middle course?

Answer 19

The river has a V - shaped vertical erosion decreases and lateral erosion increases. The river starts to erode its bank and become wider.

Question 20

What is a lower course?

Answer 20

The river has a wild shape. Lateral erosion continues, deposition takes place on the bed resulting in a shallow wide river.

Question 21

What is a waterfall?

Answer 21

A water fall is the vertical movement or flow of water. They form when a river flows over areas of hard (resistant) rock onto areas of soft rocks (non-resisant) The soft (non-resisant) rock is eroded faster than the harder (resistant) rock. This causes hard rock to overhang then the water starts to flow vertically of downward with increased velocity.

Question 22

What are two examples of waterfalls?

Answer 22

Kaituer Falls, Guyana & Angel Falls, Venezuela

Question 23

How are rapids formed?

Answer 23

Rapids maybe formed in many ways. Rapids tend to form in younger streams, with water flow that is straighter and faster than in older streams. Softer rocks in the streambed erode, or wear away, faster than harder rocks.

Question 24

What is a meander?

Answer 24

A meander is a curve or bend in the river.

Question 25

How are meanders formed?

Answer 25

Meanders are formed in the middle course of a river. As the river gains more velocity, the water is pushed to the outside of the river, causing more erosion on the outside bend, which forms a steep river cliff.

Question 26

What is an ox - bow lake?

Answer 26

A meandering river can change its course quite rapidly. An ox box lake is a small curved lake former from an abandoned meander of the river. When this happens, the following process occurs: (1) At first, the core of the former meander forms an island. The old meander becomes a crescent - shaped channel of almost stagnant water known as a cut off. (2) Slit is deposited at each end of the cut off, so an ox box lake is formed. (3) Eventually, the ox box lake is filled in with alluvium and other material, a small depression is all that remains.

Question 27

What is a flood plain?

Answer 27

A floodplain is an area of flat land alongside a river. This area gets covered in water when the river floods. In the middle and lower course of the river, allvimum is deposited on the valley floor, mainly when river floods. They vary from a 100m to tens of kilometers across.

Question 28

What are levees?

Answer 28

Along the lower course, the river bank and even the river itself may sometimes be higher than the flood plain. A levee is a raised river bank built up from alluvium deposits and is formed like this (1) After a period of heavy rain, the river is swollen with flood water, which contains sediment from higher up the valley. The river floods the flat ground along the valley floor. (2) The flood waters move more slowly than the main Channel and cannot carry as much sediment. Most of the sediments is deposited quite near to the main river channel.

Question 29

What is a delta?

Answer 29

A Delta is an area of flat land built up from silt and alluvium where a river flows into the sea or into a lake. Many Deltas are approximately triangular in shape.

Question 30

How are deltas formed?

Answer 30

Delta's are formed most easily under the following conditions: (1) The river carries a large volume of sediment. (2) The sea is relatively calm, so the sediment is carried away by waves or strong currents. (3) The sea is fairly shallow (4) The tidal range is not too great

Question 31

What are two types of deltas?

Answer 31

Bird foot and estuarine

Question 32

What is the coast?

Answer 32

The coast is the area where the land and sea meets and interacts.

Question 33

What are the different types of shores?

Answer 33

Backshore - The area beyond the high tide mark Foreshore - The area between the high tide and low tide mark Inshore - Shallow water between the foreshore and offshore Coastline - The boundary between the land and sea.

Question 34

How are waves formed?

Answer 34

Waves are formed by wind blowing over the sea water. The friction between the wind and water surface causes the water to move in a circular or up and down motion. As waves reach close to the shore, friction between the waves and the Sea bed causes the waves to rise and become elliptical. The waves then break or full on the coast. When the waves break on the shore, the water that moves up the beach is called the swash. The water that flows back down the beach is called the backwash.

Question 35

What are the wave characteristics?

Answer 35

Crest - The top of the wave Trough - The base of the water Wave height - The distance between the crest and trough Wave length - The distance between two Crest Wave frequently - The number of waves per minute Wave period - The time it takes for two waves to pass a particular point. The time in between.

Question 36

What are constructive waves?

Answer 36

These are low energy waves that deposit sediments on the shore forming the beach. They have a strong swash but weak backwash. They carry sediments and buildup or construct the beach.

Question 37

What are destructive waves?

Answer 37

These are high energy waves that destroy or erode the beach. The swash is strong but the backwash is more powerful as it drags material down the beach.

Question 38

What is longshore drift or littoral current?

Answer 38

This is the process by which materials on the coast are transported or move down the beach along the coast. It results in the pileup of material or sediments at one end of the bay. Waves approach the beach at an angle based on the direction of the wind. When the waves break on the shore, the swash moves up the beach obliquely or at an angle. The backwash moves straight down the beach.

Question 39

How are materials transported?

Answer 39

Materials on the coast are transported from point A to point B at an angle by the swash. Then the materials is transported straight down the beach by the backwash to Point C. Then another swash carries the material from point C to point D at an angle. The backwash moves the material straight down the beach to point E. This zigzag movement is called the Longshore drift or littoral current and moves material down the beach. Groynes are set up along the beach to prevent material from being moved down the beach.

Question 40

What is wave reflection?

Answer 40

Material is deposited on a beach as a result of wave refraction. When waves enter bays, they change their shape to the shape of the coast. The energy is focused at the headlines and the weak waves deposit material on the bay forming the beach.