NWEL Flashcards
A delta has the following features
1) Naturally fertile sediments
2) Sufficient water
3) Transport routes
4) Very limited relief
Delta definition
accretion of clay, silt, sand that forms when a river debouches into a sea or lake. The velocity in a delta area is low and thus sedimentation occurs.
The NW European lowlands location
foot of the Rijns Massief and its formation has been due to tectonics, climate change, and sea level change over the past 14 million years.
the Cretaceous period time and happenings
145 -65 million years BP
sea water levels were high and the NW European lowlands was a shallow and warm sea where there was carbonate deposition
Paleogene- Neogene period (Tertiary) time and happenings
(65-2.6 million years BP) there was tectonic uplift of the Eifel and Ardennes and subsidence of the North sea basin with causes a tilt of the Netherlands since 14 million years BP. This subsidence is still going on in NL.
which Four rivers have contributed to the formation of the NW European lowlands:
1) Rhine
2) Meuse
3) Schelde
4) Eridanos (From Scandinavia)
What happened during the quarternary? (4 steps)
- First there was infilling of the North Sea basin by fluvial deposits from uplifted areas.
- Then there was large-scale building of a coastal plain, resulting in Delta formation.
- During the Late-Cromerian the Eridanos disappeared because of the presence of an ice sheet.
- Rhine deposits become dominant because of catchment growth through river capture.
When did the Rhine and Meuse start to flow to the West instead of the NW and why?
Saalian, 0.15 Ma BP
because of the presence of an Ice sheet in the North. First it was NW because of the sinking North sea basin.
Bedload:
consists of rocks, gravel and coarse sand and rolls over the bottom of the water column
Suspension:
Consists of fine sand, silt and clay particles that are suspended in the water column
Describe flow velocity patterns in a river
(deposition and erosion graph)
The flow velocity goes up there is more deposition of bigger particles. Because of cohesion this is the particle size that is deposited and eroded is first almost zero or very low. High cohesion in small particles. They stick together. A stronger force is therefore needed to erode them (a higher flow velocity).
Anastomosing river
Anastomosing Is a higher order channel pattern consisting of multiple interconnected channels that enclose relatively large islands, normally wetlands.
Braided rivers:
These rivers have a high stream power because of a high gradient and high discharge. There is much lateral erosion and that results in a wide braid plain. Bedload dominated, so mainly coarse sediment. This results in the formation of mid channel bars.
Meandering rivers:
These rivers have a moderately high streampower, focused on certain spots (buitenbocht). There is local lateral erosion and deposition. Common transports are coarse and fine sediments, so both bedload and suspended load. There is a fining upward sequence found. Deposition in inner bend (Scroll-bars) and erosion in outer bend. Oxbow lakes form when water finds a new faster way further and is cut off.
Straight rivers:
This river has low stream power and thus almost no lateral erosion. Suspended load dominates. Thea banks consists of cohesive sediments and thus erosion resistant. Not perfectly straight river, there is always slight winding.
River types in the NW European lowlands
The stream power is too low for braided rivers, they were there in the past (remnants in the South East). The meandering of the Rhine decreases downstream due to a decreasing gradient, increasing bank stability (clay and peat -> cohesion so hard to erode) and increased tidal influence. The splitting and rejoining of the river branches of the Rhine Meuse delta constitute an anastomosing river system. But this is on a very large scale.
terrace crossing
is a border between incision (upstream) and deposition (downstream), The location is determined by tectonics, climate and sea-level. Because of sea level rise the terrace crossing shifts upward.
sedimentation wedge
sedimentary fill downstream of the terrace crossing
sediments Downstream of terrace crossing
Young sedimentary layers cover old sedimentary layers
sediments Upstream of terrace crossing
Young terraces are located lower than old terraces
Important aspects of the representation of a river profile
a dynamic equilibrium between discharge sediment load and gradient and is disrupted by tectonics, sea level changes and climate change
Rivers in cold period
hardly any vegetation
snow-meltwater discahrge runs over permafrost, resulting in large pulses of sedimetn adn water
braided rivers in a wide plain
Rivers in warm period
much vegetation
relativley large discharge and low sediment load (high infiltration).
only main channels remain active (meandering)
Why does incision occur in transitions between warm and cold periods?
inbalance between water and sediment supply –> sediment hunger (water>sediment)
incision at cold to warm periods
sediment decreases, permafrost melts, vegetation appears.
the vegetation appears and hold the sediment in place and permafrost melts increasing the discharge.
incision at warm to cold transition
peak discharge increases, vegetation remains for some time.
the peak discharge increases because of snow melt water in the spring /summer.
what is the consequence of incision at climate transition points?
what happens in the landscape?
terrace formation - abandonment of part of a river plain.
How was the climate in the Late Weichselian?
climate fluctuations and instability
Terraces around the meuse
we see incision and terrace formation and a stepwise incision. Four terraces were formed during this period. Elevation differences often > 0.5 m and within the same terrace level <0.5 m. Form the Meuse multiple channels of the original braided river have incised causing an irregular landscape of terraces with several isolated valley plain terraces.
When was the Young dryas?
12,900 - 11,600 BP
What happened to the river terraces during the young dryas?
River dunes were formed
Natural levees
Natural levees form when there is deposition next to the channel bed during a flood. The thickest and coarsest sediment is deposited at the edge and further away from the streambed where velocities are low finer sediment is deposited. There is a fining upward sequence. Over time the natural levee becomes higher and it becomes harder for coarse fraction to reach the top.
Crevasse
A crevasse is a natural breach of a levee.
Crevasse splays
relatively coarse sediments deposited from a crevasse channel behind the levee in the flood basin. Gap in natural levee.
Avulsion
A sudden abandonment of a river channel and the formation of a new river channel due to breach of a levee.
Main causes for avulsion
- Decreasing discharge capacity of the main channel due to sedimentation within the river channel.
- The gradual formation of a new route through the flood basin, which has a gradient decrease. (Riverbed becomes higher compared to the natural levees and thus easier flow.)
Contributing factors for avulsion
- Ice jams
- Digging/ scouring by animals
- Strong erosion of outer banks in meander bends.
Avulsions may develop from crevasses
Many avulsions in Holocene Rhine Meuse delta went west to east over time. Why?
- Sea level rise (and thus position of the terrace crossing, which is more and more upstream).
- Discharge of water and sediments from hinterland (climate change).
- Position of faults (earthquakes etc.)
Full avulsion
The old channel bed downstream of the avulsion point is wholly abandoned
Partial avulsion
The old channel remains to carry water next to the new channel. An anastomosing river system develops. Both channels are active.
Avulsion belt
Area influenced by avulsion.
Alluvial ridge
Complex of natural levees and residual channels (old infilled river channels), which is elevated relative to the floodbasins.
Channel belt
Zone in which channel deposits of comparable age and origin occur. So where the channel has been in the past.
Brief explanation of modern embankments, floodplains and dikes
Because of the construction of dikes after 1100 AD the river channels are now fixed and embanked floodplains formed so no new avulsions are possible. However, high water levels may cause seepage behind the dike and there could be dike breaches during high water levels or a dike breach scour hole at the foot of the dike. A dike breach deposits relatively coarse sandy sediment on top of clayey subsurface.
Describe the Eastern River landscape
The eastern river landscape is characterized by age (pre-Holocene) and terrace landscape with relief of bars (high area) and channels (low area). Upstream of the terrace crossing old terraces lie higher than young terraces. River dunes were formed during the Young Dryass, cold and dry period.
Bars (different types)
unstable points in the river
scroll bar - ancient bar
point bar - actively forming
Reclamation of western river landscape up to middle ages
Along the Meuse we can find traces of Late stone age, Bronze age, Iron age and in particular Roman times. There was secondary dune formation on the top of the river dunes. In the Late middle ages, many land was used as arable land and led to drainage and defrorestation. Only the lowest areas remained untouched (swampy) forests.
landuse change for high lying sandy terraces
arable land (primarily asparagus: no gravel, humus poor, clay poor and rooting depth 100 -150 cm
land use change for high lying clayey terraces
arable land and orchards (relatively clayey) and roses and conifer cultivation (relatively sandy area)
land use change for low lying clayey terraces
Grassland and natural forest (alder and willow)
land use of river dune
pine forest, heather, birch and oak forest
LAND ID terrace landscape
Winding roads
Arable land and settlements (high)
Grass land and forest (low)
Irregular, blocky parcellation
LAND ID river dune landscape
Straight sandy roads
Heather and pine forest (dunes)
Arable land and grass land (terrace)
Central river landscape description
The higher locations of the central river landscapes have productive soils for agriculture and for this reason (and for keeping dry) early settlements were located here.
synsedimentary decalcification
The dissolution is highest at high CO2 tension. In the floodbasin during the deposition: soil water is saturated, vegetation roots produce CO2, immediate dissolution of calcium carbonate and washing out by water.
Parcellation around natural levees (central)
The parcellation at the natural levees consists of irregular blocks and that of the flood basin consists of wide strips. At the natural levees this is the most fair and at the floodbasin strips because of drainage by straight ditches.
The natural levees in this perimarine riverlandscape are narrower, lower and more clayey (compared to central) due to:
1) A lower river gradient
2) Tidal influence (gradient is lifted when tide is high)
3) Sediment depletion -> peat formation
The river basins in west are larger than centre due to:
1) Sediment depletion
2) Wide river plain
The coarser material cannot be deposited above the natural levee, only clay. Coarse sediment too heavy to transport.
Western river landscape: the agricultural landscape
An inversion landscape formed because of reclamation of the peaty floodbasins were drained which resulted in differential compaction. Elevation differences increased between alluvial ridge and floodbasin. Gradient of the river here 5 cm /km and in central river landscape 50 cm/km.
Distribution of peat in NL
There is more peatland in the North of Europe than in the South and is classified differently in different countries. 7.3 % of the Netherlands consists of peatland. Peatlands increasingly play a role in policy relating to climate change, biodiversity and other ecosystem services.
peat definition
peat is partially decayed vegetation or organic matter, accumulated in an anaerobic environment.
conditions required for peat formation
- The input of organic matter should be larger than decomposition.
- Geomorphology: flat landfrom, with accumulation of (rain) water, swamp formation
- Climate: precipitation surplus, temperature not too high (decomposition) and not loo low (no vegetation)
- Not too acid conditions (no vegetation growth) and not too calcareous (too much decomposition)
3 ways to classify peat
trophic class, hydrology, topograph
3 trophic classes of peat
eutrophic, mesotrophic, oligotrophic
based on the nutrient status of the water, which determines composition of peat-forming plants and thus the type of peat.
eutrophic peat
nutrient rich peat (muddy water, silt and clay present), pH range 6.4 – 8 and the C/N ration is <20 (rather low). Often groundwater fed. Dominant plant species: alder, reed, sedge
Mesotrophic peat
Intermediate nutrient rich peat (e.g. seepage and river /rainwater), pH range 4.8 – 6.4 and C/N ratio 20-60. Dominant plant species: sedge, birch
Oligotrophic peat
Nutrient poor peat, often rainwater fed (groundwater contains more nutrients), pH range <4.8 and C/N ratio >60. The dominant plant species for this type of peat is Sphagnum moss
Sphagnum moss
acidifies the environment. Self-regulating plant, it retains rainwater and grows into hummocks. It suppresses many other plant species and forms peat domes.
How does classification based on hydrology occur?
Position relative to the groundwater table. Fens and Bogs
Fens (1 word)
topogeneous
bogs (1 word)
ombrogenous
Fens explanation
Low position in landscape, groundwater fed peat: topogeneous, nutrient status depends on groundwater quality (oligotrophic – eutrophic)
Bogs explanation
High position in the landscape, rainwater fed: ombrogenous, always oligotrophic.
Topography - high lying peat
High lying peat landscapes are often bogs from Pleistocene cover areas, because of poor runoff from flat landforms (plateau). -> Sphagnum peat
Topography - low lying peat
Low lying peat landscapes are often below 1 m NAP. Fens have formed because of sea level rise resulting in groundwater level rise. Western and Northern coastal landscape, also perimarine landscape.
4 types of peat profiles
1) Terrestrialisation peatlands
2) Plateau peatlands
3) River plain peatlands
4) Coastal plain peat
1) Terrestrialisation peatlands
Peat forms from open water (pond, lake or heathland fens) and becomes land. The open water is often nutrient rich or mesothrophic. A eutrophic / mesotrophic fens is formed. In the peat profile layers can be distinguished. The oldest layer (calcareous gyttja) consists of very fine plant residues and algae and may contain carbonate. Detritus is eroded peat and partly decomposed (aquatic) plant residues. Terrestrialisation can also happen in nutrient poor water consisting of accumulated rain or a heathland fens and may be colonised by sphagnum.
2) Plateau peatlands
origin is in the Pleistocene coversand areas, they are bogs and ofter rainwater fed and thus oligotrophic. They form because of poor runoff from the heathland fens or brook valleys.. The plateaus are overgrown. Terrestrialisation peatlands can become plateau peatlands. Formation of plateau peat from terrestrialisation peat, because of colonisation by Sphagnum.
3) River plain peatlands
Low lying peatland that is influenced by rivers so muddy water containing silt and clay. It is a fens and becomes more mesotrophic further away from the river. Where the river does not have influence any more it is coastal plain peatland.
4) Coastal plain peat:
Is not influenced by rivers. Oligotrophic fens and leads to bog formation.
Formation of river plain peatlands and coastal plain peatlands in low lying areas (step by step)
A) Marine deposits in the coastal plain (lagoon)
B) Coast line is closed because of beach ridge formation from 6000 BP. Formation of reed peat in brackish marine clay.
C) River clay deposited along rivers: river plain peat. And in closed coastal plain: reed grows first and than sedge and then sphagnum: coastal plain peat
D) Formation of peat domes (bogs) in the coastal plain: fens have become bogs.
Suitability of oligotrophic peat
peat cutting and turf preparation
Describe the perimarine, low lying peat landscape
- Flood basins: broad, eutrophic / mesotrophic river basin peat.
- Natural levee: very narrow compared to central river landscape, flat and low, clayey, perimarine.
The History of peat reclamation, settlements, and working (bit of an essay)
The first colonisation was on the natural levees about 1000 AD. Because the natural levees are very narrow they quickly moved also to the flood basins (river plain peatlands). The land was divided according to the ‘Cope’- parcellation with exact dimensions: 1250 m x 115 m. The ditches that mark the border of the strip parcels are very wide. The strips were parallel to the river and perpendicular to other strips. By signing the Cope contract you were allowed to do agriculture in name of Utrecht.
As soon as you start to use the area as arable land, subsidence takes place. Because of reclamation the groundwater level was lowered causing physical ripening, which causes the volume of peat to decrease. There was also oxidation (chemical ripening) which lead to the decomposition of peat. With wetter conditions, there is further drainage and further groundwater level lowering.
After the groundwater level lowering (and peat erosion) there was sea ingression and increased storm activity causing the formation of lakes. For this reason people started building dams and that’s how Amsterdam has formed
‘Cope’- parcellation
1250 m x 115 m
physical ripening of peat
causes the volume of peat to decrease.
chemical ripening of peat
oxidation which lead to the decomposition of peat
Inversion landscape
when the sediment layers change height
Which parts of the Netherlands are subsiding?
- Peat areas
- Clay areas
- Gas fields in Groningen
Sandy areas do not subside. Tectonic subsidence is not yet included.
To improve the topsoil of the low lying peat areas for agricultural use an imported top layer was used to increase the bearing capacity. This layer consists of:
- (organic) dredge
- Stable manure and sand
- Household waste
The advantages of using oligotrophic peat rather than mesotrophic or eutrophic peat for turf has several reasons:
1) High calorific value, contains relatively much carbon (high C/N ratio)
2) Little ash because there is no silt and clay present
3) Little stench
(droogmakerijen)
In the same time water was extracted from artificial shallow lakes. These reclaimed lakes (droogmakerijen) were used for agriculture. It is marine clay with a peat cover.
What was the result of all the peat working etc.?
impact on human economy
This results in energy from coastal plain peatlands, food production on the river plain peatlands. First there was peat cutting and later peat dredging.
What happens to the soil with distance from the river in peat formation?
Clay gets thinner further away from the river and thus the trophic class also becomes lover (eutrophic - > mesotrophic).
Land use and identity: natural levee lowlying peat landscapes
- Open, flat, slightly sloping
- Linear settlements on the dikes
- Winding roads and dikes along peat rivers
- Many narrow water bearing ditches
- Narrow strips ‘Cope’ parcellation
- Grassland
- Trees near buildings only4
Land use and identity: peaty flood basin:
- Open, very flat
- Linear settlements parallel to each other
- Straight roads parallel
- Many straight and broad ditches
- Narrow strips parcellation (‘Cope’ parcellation)
- Grassland
- Trees alongside roads and near buildings
What did NL look like in the Holocene?
Within the Holocene there are more wet and dry periods. In the beginning of the Holocene the Netherlands was a sand landscape with a low sea level, braided rivers, but a deeper sealevel than worldwide because of the subsidence.
What happened around 6000 y a?
Around 6000 – 7000 BP there was a transition from rapid to slow sea level rise. There are regional differences between sea level curves because of difference in subsidence. Because of the subsidence we speak of relative sea-level rise increases.
Transgression
coastline shifts landward which leads to the deposition of marine sediments in a coastal plane.
Regression
the coastline shifts seaward and leads to peat formation in coastal plain.
Basal peat:
10,000 y a
With sea level rise the groundwater table rises as well and can reach the surface. This leads to peat formation. Based on the layers in the peat we can reconstruct how fast the sea level has risen in this period.
Beach ridges
6500 - 2000 y a
Beach ridges are sand bars parallel to the coast that have been deposited up to a level permanently above sea level. The conditions for this are:
1) Sufficient sand present
2) Wind driven wave action on the coast
3) Gentle submarine slope near the coast, which breaks wave and thus facilitates landward transport of sand.
4) Coastal parallel current (migration of sand, longshore drift)
Beach plain:
whole history of transgression and regression as well :)
6500 – 2000 y a
A beach plain is a low lying area in between two beach ridges. It is a beach locked off from the sea.
The oldest beach ridges are more land inward and lower. Around 6500 – 2000 BP there was the formation of a coastal barrier consisting of beach ridges and beach plains. From 7500 – 5850 BP there was transgression and after that regression starts again. 5850 BP is a turning point. A seaward shifting coastline from that point. There was fresh water behind the coastal barrier (peat formation).
Old dunes formed on the beach ridges through aeolian displacement of beach ridge material and are smaller than 10 m. They formed until the early middle ages. Primary dunes!
Basal peat is below marine deposits.
Old marine clay:
Formed from 8000 – 4000 BP. Lagoon and tidal flat depostits in tidal basins (behind coastal barrier). Sea water enters via inlets. Close: sand deposits and further away clay deposits.
Holland peat formation:
6000- 1000 BP: formation. Fresh water conditions developed behind coastal barrier and caused formation of peat. There was a rising sea level resulting in groundwater level change. Peat bogs formed. Along small rivers there was eutrophic riverplain peat and farther away from river oligotrophic coastal plain peat with sphagnum peat domes. Old marine deposits become thinner more landward.
Young marine clay
Formed around 4600 BP – recent because of erosion of the coastal barrier and ingressions in the peat area behind it. The most ingressions were between 250-600 AD and around 1200 AD. There were stormy weather conditions which caused ingression.
Amphidromic points
Around these points the tide difference is equal to zero. Further from that point the tidal difference is bigger. The western coast (holland) of the Netherlands is very close to an amphidromic point so micro tidal differences (<2 m). In the northern Netherlands there is a mesotidal rage (2-4 m). In Zeeland there is also a meso tidal range (2-4 m). The areas with a mesotidal range have an open coast line and Holland has a closed coastline (micro tidal range).
Young dunes
Young dunes are secondary dunes formed around 800 AD – present. They formed because of coastal erosion because of the high storm activity and remobilisation of old dunes. Because of erosion high supply of sand to the beach. Aeolian deposits and deposition of beach sands. Because of the coastal erosion also caused steepening of submarine slopes and the eroded material is placed on land as dune. Deposition of beach sands. Because of elevation differences have a different soil. Can also be redeposited old dunes. 40 – 60 m high.
Secondary dunes
aeolian deposits from beach plain
Primary dunes:
Formed by sand from beach ridge
Differences in dunes around NL
Young dunes in Zeeland are narrower than in Holland. They were only formed after intense coastal erosion since 3rd century.
Utilisation of beach ridge
The beach ridge area is often used for flower bulbs cultivation. Flower bulbs need a ground water level of 55 cm. The water level is controlled and beach ridges were excavated for this. Calcium carbonate is present from clay deposits.
Landscape identity of beach ridge (not excavated)
Woods, estates
Villages and cities
Old and aligned with beach ridge (bit winding)
Forest
None
None
Low old dunes (<10 m)
landcape identity of beach plain
Grassland
Absent
Few, no old roads
Absent
Many straight ditches with a high water level
Strip parcellation
Flat
Uses of the dunes
The young dunes are primarily used as coastal protection, nature conservation areas, drinking water production (through biological purification of infiltrated river water), recreation and tourism. At the shore zone marram grass in planted to trap aeolian sand. There is a lot of ecological variability in the area because of topographic variability. For example, there is a difference in moisture and wind conditions.
The requirements for flowerbulb cultivation are
- A water table of 55 cm below the ground level. This 55 cm is because of the fact that capillary rise in medium sand is very low and because of a shallow rooting system. The water level Is kept at this level using ditches.
- Sandy, calcareous soils
More info on flower bulb cultivation:
soil activity and type, describe horizons
The houses are normally located on the remaining beach plains. peat
The soil we find in this area is a calcareous Enk soil, formed by excavation and deep digging every 3 to 4 years. The A horizon is thicker than 50 cm.
Loess landscape in the cretaceous
(145 – 65 Ma BP) Krijt: Formation of limestone because of calcium carbonate skeletons accumulation in the shallow see. There is layering within the limestone. The time period of a layer can be determined by fossils, remains of organisms. The Mosasaurus lived in this period. High sea level because of high CO2 levels due to volcanism and high tectonic activity. Mergel is wrong name because it means it consist of 90 % clay and 10 % calcium carbonate but it’s the other way around.
Loess in the tertiary (paleaogene and neogene):
Uplift of the Eiffel, the Ardennes and South of Limburg. The North Sea basin went down, which was the origin of the North Sea. The tectonic uplift happened at an uneven rate. There was alternation of glacials and interglacials resulted in incision and the formation of terraces. Origin of alluvial fan of the Meuse which brought gravel, coarse sand. In this period river terraces formed.
Loess in quarternary to saalian
(2.6 – 0.38 Ma BP): Meuse deposits on top of river terraces: gravel and coarse sand. Close to where sediments come form so severely coarse. The Meuse migrated as a result of oblique tiling. The West of South Limburg uplifted at a lower rate and that’s why the river terraces are best preserved at het East of the Meuse. In total 34 terrace levels. The terraces in the South are different than in the North because in South oblique tilting and climate cycles and in the North only climate cycles. There are dry valleys across the Southern terrace landscape formed by discharge of snow and meltwater. Water could not infiltrate due to frozen subsurface present.
loess in saalian and wichselian
( 0.38 Ma – 11.400 BP): Loess deposits in a periglacial environment. Makes terraces harder to recognise. 80% silt, 15 % clay, 5 % sand
ripening in loess
not applicable - not deposited in a wet environmen
decalcification in loess
to a few meters depth, rainwater acidifies
brownification in loess
yes, MHG is deep, decalcified, weathering of minerals
clay translocation in loess
yes, downward movement of water and pH 4.5 - 6.5
podzolisation in loess?
no, is nutrient rich
gleying in loess?
no unless water stagnates on the brick layer
homogenisation/ PHCP in loess?
Yes, attractive soil for soil animals, well drained unless there is a brick layer, which can interrupt.
Loess on different sloping landscapes
On flat terraces the (slope < 2 %) the Loess package is thick and fully intact. On slopes (>2 %) there is erosion of Loess on bare arable land. Loess is picked up and accumulates on the foot of the slopes for example in a dry valley. This accumulation of Loess together with sometimes gravel and limestone is called a colluvium. Often also mixed with remains of settlement (eg. Flint, pots, bones). On slopes steeper than 16 % there is erosion and the limestone crops out, Loess is almost absent.
colluvium
This accumulation of Loess together with sometimes gravel and limestone
landuse flat terrace plateaus loess
On the nearly flat terrace plateaus there is a varied land use unless there is water stagnation on a brick layer. Good for agricultural land
steep slopes >16% land use loess
On the steep slopes >16 % the landuse is forest (deciduous woods). It is too steep for agriculture because of susceptibility to wind erosion and very stony.On slopes dominantly grassland.
lynchets
bush rows intended to trap eroded material. They cause the formation of mini terraces. The lynchets are valuable from a cultural historical point of view and ecological point of view.Made on loess slopes.
Cause of sunken lanes
Sunken lanes are caused by erosion of unpaved country roads on steep slopes (terraces edges, dry valleys).
Landscape Identity Brook valleys loess
In the brook valleys there is little settlement, roads, dominantly grassland (periodical inundation), irregular parcellation, isolated trees and groves: alders, willows, and poplars.
Where are villages built in the loess landscape?
flat plateaus using limeston
What happened to Dutch rivers during the 20th century?
In the first half of the 20th century in the Netherlands a few rivers were changed from a straight river to a meandering river. This is a measure taken to mitigate desiccation (verdroging).
Where are loess and sand landscapes found?
The Pleistocene Loess landscapes are only found in the South of Limburg. The sand landscapes are primarily found in the North, East and middle of the Netherlands.
How is the Pleistocene subdivided?
The Pleistocene (2.6 Ma BP) is subdivided into warmer and colder periods. It is the only period that is based on climatic conditions instead of fossils of different species. Climatic conditions are determined based on oxygen isotopes stages.
explain how Climatic conditions are determined based on oxygen isotopes stages
In cold periods O16 evaporates easier than O18 and is fixed in the ice sheets. O18 is left in the sea water and thus a relatively high concentration compared to warmer conditions. In the ocean organic carbonate skeletons are examined that have accumulated on the ocean floor. The change in the ratio O18 / O16 in deep see sediments and ice sheets are measures of climate changes.
Saalian important!
two time periods!!
During the Saalian (380.000-130.000 BP) there is an ice sheet cover in the Netherlands. The corresponding isotope stage is 6 (180.000-130.000 BP).
Glacial period
Prolonged dominantly cold period (ice age). Order of magnitude 100 000 years
Stadial period
coldest part of a glacial period (bare / tundra vegetation). Order of magnitude 1000 years
Interstadial period
short warmer period in a glacial period (dwarf -bushes)
Interglacial period
prolonged dominantly warm period (forest)
How do glacial period transitions occur?
gradually
What causes cold and warm periods?
Milankovitch cycles
Ice lobe ridges and basins in the Saalian (6)
The extent of ice sheets in Saalian (380.000-130.000 BP) during stage 6 (180.000-130.000 BP). Only time when ice sheet reached the Netherlands. Ice lobed preferably move through river valleys, for example the Ijssel valley. The order of magnitude of the thickness of the ice is around 200 m. Movement and scouring of ice lobes cause pushing and tilting of strata of frozen fluvial sediments. Ice pushed ridges (for example: Wageningse Berg) and ice lobe basins originated. Now the ice lobe basins have been filled up by for example coversand etc. but it could have been as deep as 50 -100 m order of magnitude.
Deposits during teh Quarternary
During the Quaternary (until 500.000 BP) the Netherlands is a Delta of large rivers. The Eridanos brought coarse white sands form the east. This sediment was mineralogically poor because the material older and all nutrient rich sediment has been eroded already. The Rhine and the Meuse brought brown sands of Southern origin and occasional clay. These deposits were mineralogically richer than that of the Eridanos river. Near the boundary of the pushed up sediments of Eridanos and Rhine- Meuse there is a wide zone of alternating poor and rich pushed sands.
Ground moraine
We find ground moraine deposits in Northern NL
Boulder clay
Boulder clay is deposited on the bottom of ice lobe basins. We often find this closer than 1 m below ground level. The boulder clay is very heterogeneous, it contains clay, silt, sand, gravel and boulders. The layer is very compacted because of the weight of the ice.
dump moraine
A dump moraine is a hill/ ridge of boulder clay deposited near a stationary ice front. The boulders found were used to make Dolmens (Hunnebedden). The difference with an ice pushed ridge is that a at a dump moraine sediment that is transported by the glacier is deposited and with an ice pushed ridge the glacier pushes sediment that is already there to make a small hill.
Boulder sand
include the two time periods required in the formation
Boulder sand is a weathering residue of boulder clay. It often covers boulder clay and is around 10 -60 cm thick. During the Eemian (130.000 – 112.000 BP) there was more vegetation compared to the Saalian (380.000 – 130.000 BP) which created porosity and weathering of the boulder sand. During the Weichselian there was erosion of the weathered material by snow-melt water and wind action, which caused partial loss of the fine fraction (silt and clay). The nature of the residue is dependent on intensity of erosion. It can be loam-poor to loamy and fine to coarse sand and gravel.
sandur
A sandur plane is a ice-melt water fans composed of coarse sandy fluvioglacial deposits. It is behind a breach of the ice pushed ridge/ dump moraine.
Land forms from the Saalian
ice pushed ridges and ice lob basins
boulder clay
dump moraine
boulder sand
sandurs
ground moraine
Weichselian (time)
112.000 – 11.600 BP
Situation in NL during Weichselian
During the Weichselian (112.000 – 11.600 BP) there was no ice sheet in the Netherlands but the country was surrounded by ice. During this period the county had a Periglacial climate. It was very cold but there was not often ice present. There was al lot of variability in climate within the Weichselian period. It can be devided in stages:
The 5 stages of the Weichselain
1) Eemian and Early Glacial (stage 5) 112.000 – 72.000 BP: warmer and first stadials -> Weatering of Boulder clay and pedogenesis
2) Early Pleniglacial (stage 4) 72.000 – 60.000 BP: cold -> Boulder Sand, formation/ incision of brook valleys
3) Middle Pleniglacial (stage 3) 60.000 – 26.000 BP: temperate
4) Late Pleniglacial (stage 2) 26.000 – 14.700 BP: cold -> Fluvio-aeolian deposits, old coversand, boulder sand
5) Late Glacial (stage 1) 14.700 – 11.400 BP: signal Holocene – alternation cold and warm periods. -> young coversand
LGM
LGM = Last Glacial Maximum: lowest world temperature during the Weichselian. This was during stage 2 of the Weichselian.
What is cryoturbation
plastic deformation
how does cryoturbation occur?
Because of freeze and thaw processes in the winter – summer in cold and wet conditions there is folding of soil material. The seasonally frozen layer is the active layer. This layer will freeze again from the top down during the winter. The layer under it gets under pressure. Because of the wet conditions the soil is saturated with water and can easily be deformed. Movement is due to differences in density.
conditions required for cryoturbation
permafrost (mean annual air temperature -4 degrees Celsius) and cold and wet conditions.
what are frost cracks/ wedges
Brittle deformation
conditions required for frost cracks and wedges
mean annual air temperature: 0 degrees Celsius and dry conditions
how do frost cracks and wedges form?
First frost cracks form because of freeze-drying of the soil under cold and dry conditions order of magnitude cm. These cracks may develop to frost wedges, order of magnitude cm – dm. When the ice in the frost crack is gone it can fill up with soil material. And when ice forms again the crack will expand and when the ice is gone again it can fill up with soil material again. A Ice wedge is a frost crack filled with ice.
Dry valley
alley in which under present conditions now water flows because of lacking permafrost. Formed by erosion of sloped terrain when permafrost inhibits infiltration of water. Discharge snow.
What is a pingo?
Mounds of up to 50 m high and 500 m across consisting of an ice core covered by soil that has been pushed upward by the ice.
How does a pingo form and what are the two methods of water supply?
when the ice melts, a hole remains encircled by a ridge of ground, which was slided of the top. (fossil pingo) There are two situations with different water supply:
1) A frozen upper layer with subsurface supply of groundwater because of hydrostatic pressure form neighbouring higher grounds. (seepage)
2) Plateau type: In flat areas permafrost may put pressure on deeper groundwater with is squeezed upward through cracks in the permafrost. (cryohydrostatic pressure)
Brook valley history - timing and order!
During stage 4 (Early Pleniglacial) brook valleys formed because of the snow-meltwater flow over the permafrost. There was a strong sea level fall which caused an increase in flow energy resulting in incision. During the Late Pleniglacial the brook valleys were filled with fluvio-aeolian deposits (coversand, blown or washed in, very stratisfied, fine fraction of boulder clay. Upper part of the boulder clay becomes boulder sand.
General characteristics of Coversand and fluvio-aeolian deposits
- Aeolian deposit in a periglacial environment
- It is a local process of drifting of sand in a bare to sparsely vegetated environment (tundra vegetation) landscape
- Well sorted fine sand (possibly silt)
- Well rounded grains (feels soft) as a result of saltation
Aeolian deposits sand and loess - late pleniglacial facts
: old coversand (wet deposited)
Aeolian deposits sand and loess - late pleniglacial details
- Composition: strongly layered, thin sand and silt layers (loamy)
- Climate: wet (snow) and cold, adhesion of sand to wet surface, silt falls out of suspension. Sand gets deposited and silt settles later. Because of this layered.
- Geomorphology: wide spread, flat, relief max 0.5 m
aeolian deposits late glacial facts
young coversand - dry deposits
aeolian deposits late glacial details
- Composition: weakly layered sand (loam poor)
- Dry conditions are needed, permafrost not continuous anymore so water could easily infiltrate.
- Climate: dry and cold (polar desert)
- Geomorphology: ridges/ parabolic dunes (height 0.5 – 1.5 m) along and around ice pushed ridges (sand is easily trapped) coversand belts may occur. Coversand ridges are parabolic dunes open to the west where the wind comes form.
aeolian deposits late pleniglacial
Composition: strongly layered, combination of aeolian and water laid deposits such as old coversand, water displaced coversand, eroded boulder clay/ sand fractions.
- Climate: alternation of wet, cold (coversand) and less cold (thawing of upper layer permafrost and surficial erosion)
- Geomorphology: in brook valleys
Differences between coastal landscape and marine clay landscape
coastal - Directly along the shoreline vs. marine clay - Behind beach barrier
coastal - Sandy subsurface vs. marine clay - Dominantly clayey subsurface
coastal - Relatively rich relief vs. marine clay - Relatively subtle relief
How do we divide marine clay landscapes
The subdivision of the marine clay landscapes is based on coastal morphology, which depends on the tidal range and storm activity. The tidal range depends on the distance to the amphidromic points. At this point the tidal difference is equal to zero.
geological timeline - 6500 y a
After 6500 BP the coastal barrier formed and there was deposition of old marine clay in the back-barrier tidal basin.
geological timeline - 6000 y a
After 6000 BP peat forms in the freshwater coastal plain behind the prograding and closing coastal barrier.
geological timeline - 4600 y a
From 4600 BP until recent there is deposition of young marine clay because of erosion of the coastal barrier and ingression s in back-barrier peatlands.
geological time line - 250-600 AD and 1200 AD
The highest storm activity was observed around 250-600 and around 1200 AD. In the Southwestern Netherlands a large land loss has occurred due to storm surges (1573 AD).
old land
Parts of the land that have never been eroded are called ‘old’ land and in many places peat remains in the subsurface.
why did beach ridges and peaty coastal plain in SW NL erode?
high storm activity
Consequences of high storm activity in 200-1000 AD in SW NL
Because of the high stormactivity (200 -1000 AD) the beach ridges and peaty coastal plain in the SW NL eroded. The veenstroom becomes a tidal creek. Because of the occasional flooding creek ridges form, which look like natural levees. Clay was deposited. The peat compacted due to reclamation. Further away from the creek smaller pools originated which were old ditches and because of this reason the pools and the creek ridges have a straight pattern. ‘Old’ land was created consisting of creek ridges (oeverwal) and pools (slootjes). We can find a fining upward sequence. On the creek ridge we find sandy clay and in the pools we find heavy clay on peat.
What was done with old reclaimed land SW NL?
Form 12th -20th century AD there was further reclamation of ‘old’ land. In the middle ages salt was extracted form the peat that has been saturated with salt water during flooding. This is called darinkdelven, moerneren or selneren. This resulted in an uneven ground surface with clay remaining a bit higher. After reallocation of the parcels the ground surface was levelled again.
How did salt production work?
1) Peat was mined and burned in a special oven
2) Water was added to the ash
3) After boiling the salt remained
How was new land created?
The formation of ‘new’ land started in the 12th century. Which was a stepwise process of renewed silting up and embankment. The sea level is still rising so the new claimed land that formed was higher lying than the ‘old’ land.
Vertical accretion
flat surrounded by water
Lateral accretion
Deposition against a dike, a fining upward sequence can be found
sand flat
We start with a sand flat with wave ripples, no vegetation, < MHW (mean high water)
mud flat
The sand flat becomes higher and becomes a mud flat with a clayey cover and is weakly vegetated, around the height of the MHG.
salt marsh
If it fully develops, a salt marsh is formed which only floods with storms. The height is above MHG. There is much vegetation. You see where the creeks are located. A younger salt marsh is higher because of sea level rise. Closer to the sea the sea primarily sand is deposited. Further away there is sandy clay on sand and furthest away we find clay and sandy clay on sand. So we find a fining upward sequence.
to which other land form does the old land resemble?
When there is more drainage, there is more biological activity and thus more mixing. The ‘old’ land have some similar characteristics as the central river landscape. Soil conditions are variable. Creek ridge can be used for storage of fresh water. During drought you can pump it up
land use id for creek ridge
Convex toposgraphy, varied land use, villages and old farm houses, winding roads and ditches with low water level, trees along roads and at buildings, irregular blocks parcellation. Creek ridge has same land use.
land use identity for pools
Flat and wet, lot of ditches, grassland, parcellation still irregular blocks because creek ridges are irregular, no trees, old peat spots water can reach surface.
land use identity new land
Land use identity:
- Slightly sloping
- Not too many ditches because of the use of drainpipes. Low water level in the ditches.
- Not many settlements
- Straight roads
- Productive arable land.
- No trees, only around houses and on inner dikes
- Large regular blocks parcellation
what is the central marine landscape?
The central marine clay landscape comprises the marine landscape behind the coastal barrier between Hoek van Holland and Den Helder. It consists of old reclaimed lakes from 1500 – 1900 AD (polders) and young reclaimed lakes, the Ijsselmeer ‘polders’. West Fiesland and the Northern wide part of North Holland belong to the central marine clay landscape as well.
when did the old lakes form?
1500-1900 AD
The history and facts of old reclaimed lakes
Consist of reclaimed ‘polders’ which are drained lakes and gained land in the Western Netherlands. In the West the coastal plain peat has been excavated for turf winning and now the underlying marine clay is at the surface in so called ‘geological windows’. Oude droogmakerijen originate form pumping dry the peatland lakes between 1500 and 1900 AD. People started to settle on the old marine clay. The trophic class of the peat determines the location of the reclaimed lakes. Oligotrophic Sphagnum peat domes were located farther form the rivers and less nutrient rich. Sphagnum peat is very suitable for turf winning. Eutrophic river plain peatlands remained.
Where are oligotrophic sphagnum peat domes located
further away from the river - tehy are less nutrient rich.
How does peat trophic class impact which ones were kept and which ones given away?
Sphagnum peat is very suitable for turf winning. Eutrophic river plain peatlands remained.
Which 3 systems were in place in between beach ridge islands?
There were three systems in the tidal basin with associated tidal inlets between beach ridge islands: Rijswijk system, Haarlem – Hoofddorp system and the Beemster – Hauwert system. However from 4750 BP the open coast system changed to a closed and prograding coast.
How were teh coastal deposits during teh open part of the tidal system? And when ?
4750 y a
When the coast was open in the central part of the tidal system sand and sandy clay was deposited, much accretion. Further away from the inlet in the distal part of the tidal basin heavy clay was deposited (modderklei), with little accretion (floodbasin). In the floodbasin areas reed marshes with heavy clay were located and in the tidal basin sandy and clayey tidal flats
katteklei
acid sulphate soils
when did katteklei form?
when pyrite was present
what are teh conditions for pyrite formation?
1) Water containing iron and sulphate (seawater)
2) Sulphate reducing bacteria
3) Permanently reduced environment, so almost always submerged
4) Much organic material (for example, reed marshes or mangrove forests)
how are acid sulphate soils/ katteklei formed?
- In a brackish sedimentary environment, for example the back of the tidal basin reed marshes form.
- Pyrites are formed by bacteria
- Because the lake is reclaimed there is oxidation of pyrites and formation of sulphuric acid (H2SO4)
- In the back of the tidal basin there is synsedimentary decalcification so there is not CaCO3 present and because of this the sulphuric acid is not neutralised.
- pH < 3.5
- Jarosite forms, which are pale yellow mottles in the soil.
land use identity of old reclaimed lakes
flat,
grassland,
village centres on narrow linear strips of peat upland (reclaimed from artificial lakes, plassen) or rationally laid out young villages reclaimed from natural lakes (meren),
straight roads,
no trees and bushes,
many narrow ditches with high water level,
strip parcels
Introduction to young lakes
Located at the Ijsselmeer. The Ijssel meer was not always there. It was first a flevo lake with fresh water, it was closed for the sea. Later it became open for the sea and it became a salt water lake.
Late Glacial 14.700 – 11.400 BP Weichselian
signal Holocene – alternation cold and warm periods. -> young coversand
Late Pleniglacial 26.000 – 14.700 BP: Weichselian
cold -> Fluvio-aeolian deposits, old coversand, boulder sand
Middle Pleniglacial 60.000 – 26.000 BP: Weichselian
Temperate
Early Pleniglacial72.000 – 60.000 BP: Weichselian
cold -> Boulder Sand, formation/ incision of brook valleys
Eemian and Early Glacial 112.000 – 72.000 BP: Weichselian
warmer and first stadials -> Weatering of Boulder clay and pedogenesis
