Transcript Hydro 1 - Clydebank High School

Hydrosphere
Atmospheric Water 0.001%
Ice 2.15%
Soil water 0.005%
97.2%
Ground Water 0.62%
Ice storage
condensation
Precipitation
Evapotranspiration
Evaporation
Infiltration
Water Table
Percolation
Hydrological Cycle
•
Evaporation: The transfer of water from the sea to the air as water vapour.
•Condensation: Water vapour (gas) changes back into water (liquid). It forms
small droplets which are visible as clouds.
•Precipitation: Water falls to earth as either liquid (rain) or in a frozen state
(snow, hail).
•Stream / Surface Run Off: Most water returns to the sea in the form of
rivers.
•Evapotranspiration:
•Transpiration: The transfer of water from plants to the air as water vapour.
•Ground water Flow: Some water returns to the sea as groundwater through soil
and rocks.
•Infiltration: The point at which rainfall seeps into soil.
•Percolation: The seepage of water downwards through rocks.
•Throughflow: The movement of water downwards through soil back to the sea.
•Groundwater Zone: Storage area for water which is slowly released back to
the sea via springs and rivers.
River Basins
• Aims
Describe and explain the formation of key
features of a rivers course with reference
to specific erosional processes.
The Drainage Basin
The basic system of surface drainage is known as a river basin. This
consists of a complex interaction of components which include rainfall,
channel run – off , surface streams, soils, slope, solar energy, groundwater
storage, evaporation from surface and evapotranspiration from vegetation.
The system returns water to the oceans and seas as part of the
hydrological cycle.
River Basin
Source of River Clyde
Watershed of River Clyde
(boundary between basins)
Tributary
of River Clyde
Confluence
of River Clyde
and tributary
Estuary of
River Clyde
Flood plain
Mouth of
River Clyde
Sea
Source
of river
Aims
Upper
Course
Describe the physical characteristics
of a river and its valley
Explain the formation of waterfalls,
Vshaped valleys, meanders and
oxbow lakes.
Middle
Course
Lower
Course
How rivers erode
 HYDRAULIC ACTION / Water and air are forced
into cracks on the river bank, exerting a pressure. When
this process is repeated many times it causes erosion.
 ABRASION The material carried in the
river wears away the river bed
 ATTRITION As the pebbles carried by
the river crash into each other,they
become smaller and rounder
 SOLUTION
The water in the river
dissolves the minerals in the rocks
Leave a space between each to draw a picture of the
types of erosion.
How rivers transport
Traction
Suspension
Rolling stones along the river
bed.( needs lots of energy)
Clay sized particles are carried
along by the river flow
river flow
Saltation
Sand sized particles
bounce along the riverbed
Solution
Some minerals are dissolved
by the riverwater
Upper Course
Middle Course
Lower Course
Characteristics
Slope
Upper Course
usually steep
Middle Course
Lower Course
quite steep
gentle
Width
narrow
quite wide
wide
Depth
shallow
quite deep
deep
Straightness winding
meandering
Type of load
Main work
Valley width
large/small
angular
medium/small
rounded
big meanders
small+
rounded
erosion
Transportation transportation
transportation
deposition
narrow
quite wide
wide
FEATURES OF THE UPPER
COURSE
V-SHAPED VALLEYS WITH
INTERLOCKING SPURS
POT HOLES ON RIVER BED
WATERFALLS AND RAPIDS
Upper Course
In the upper course of the river the gradient is very steep and the river when flooded is
fast flowing causing hydraulic action. The sides of the valley are steep and the main
work is erosion.
The erosion process is greatest during periods of heavy rainfall as the river has more
energy to affect the bedload as material is transported either by being rolled (traction)
and bounced (saltation).
Upper course is also affected by climate (freeze – thaw), rock types (soft & hard), local
vegetation and slightly acidic rain (corrosion) causing a chemical reaction which erodes
away rock.
Interlocking spurs are fingers of hard rock that
the river cannot erode, so it flows around them.
Potholes are holes eroded in the river bed by
stones being spun in the water (abrasion)
So how does a v-shaped valley form?
1. Vertical erosion (in the form of abrasion,
hydraulic action and solution) in the river channel
results in the formation of a steep sided valley
2. Over time the sides of this valley are weakened
by freeze thaw weathering processes and
continued vertical erosion at the base of the valley
3. Gradually mass movement of materials occurs
down the valley sides, gradually creating the
distinctive v-shape.
4. This material is then gradually transported away
by the river when there is enough energy to do so.
As the river flows through the valley it is forced to
swing from side to side around more resistant rock
outcrops (spurs). As there is little energy for lateral
erosion, the river continues to cut down vertically
flowing between spurs of higher land creating
interlocking spurs
So how does a v-shaped valley form?
1. V________ erosion (in the form of a________,
h____________ action and solution) in the river
channel results in the formation of a steep sided
valley
2. Over time the sides of this valley are
w____________ by f________ t_________
w_____________ processes and continued
vertical erosion at the base of the valley
3. Gradually m_______m____________ of
materials occurs down the valley sides, gradually
creating the distinctive v-shape.
4. This material is then gradually transported away
by the river when there is enough energy to do so.
As the river flows through the valley it is forced to
swing from side to side around more resistant rock
outcrops (spurs). As there is little energy for lateral
erosion, the river continues to cut down vertically
flowing between spurs of higher land creating
interlocking spurs
Key Term Check
V-shaped Valley - a valley
which resembles a 'v' in
cross section. These
valleys have steep sloping
sides and narrow bottoms.
Interlocking Spur - spurs
are ridges of more resistant
rock around which a river is
forced to wind as it passes
downstream in the upper
course. Interlocking spurs
form where the river is
forced to swing from side to
side around these
http://www.cleo.net.uk/resources/displayframe.php?src=308/consultants_resources%2F_files%2Fintespur2.swf
Waterfall formation
http://www.school-portal.co.uk/GroupDownloadFile.asp?file=21604
WATERFALL
RETREATS . UPSTREAM
.
. .
OVERHANG
UNDERCUTTING
OF SOFT ROCK
PLUNGE
POOL
Picture Paragraph
• The river will slowly undercut the hard rock by eroding
the soft rock underneath it.
• This is enhanced by the swirling of broken rock in the
plunge pool underneath the over hang.
• The combined effect of falling water and the swirling rock
erodes downwards – abrasion – and backwards
Hydraulic action.
• As the overhang gets larger and protrudes further it will
collapse under is own weight.
• The rock from the overhang will further erode the plunge
pool.
• Repeated overhangs and collapses over time will result
in a narrow, steep sided gorge.
1.Continuous erosion by the river will see the gradual undercutting of the slower
eroding hard rock by the quickly eroding soft rock.
2.This is enhanced by the swirling of broken rock (eroded rock) in a plunge pool
underneath an overhang.
3. The combined effect of the falling water and swirling rocks is to erode downwards –
abrasion – and backwards- Hydraulic Action.
4. As the overhang gets larger and protrudes further it will eventually collapse under
its own weight to form a new cliff.
5. The rock from the collapse will then be used to erode the resulting cliff and enlarge
the plunge pool.
6. Repeated over time a series of overhangs and collapses occur, resulting in a steep
sided & narrow gorge being formed.
FORMATION OF A WATERFALL
1.Continuous erosion by the river will see the gradual u_______________ of the
slower eroding hard rock by the quickly eroding soft rock.
2.This is enhanced by the s_____________ of broken rock (eroded rock) in a
p_________ p__________ underneath an o_______________.
3. The combined effect of the falling water and swirling rocks is to erode downwards –
a_________________ – and backwards- H_____________ A_____________.
4. As the overhang gets larger and protrudes further it will eventually c____________
under its own w___________ to form a new cliff.
5. The rock from the collapse will then be used to erode the resulting cliff and enlarge
the p__________ ___________.
6. Repeated over time a series of overhangs and collapses occur, resulting in a steep
sided & narrow g________ being formed.
MEANDERS
Meanders
Flood plain
© Used with the permission of the Geological Survey of Canada
Available at
http://sts.gsc.nrcan.gc.ca/clf/landscapes.asp
NARROW MEANDER NECK
FUTURE
OX-BOW LAKE
tributaries
V shaped valley
Steep
Valley
sides
meander
ox-bow
lake
Flood
plain
Reproduced with the permission of the Controller of HMSO
© Crown Copyright NC/02/15232