Norwich city walls are there for all driving around the inner ring road to see. The City Wall witch formed a 2 1/2mile (4km) defensive barrier around the city. In a circuit stretching from Carrow around Norwich, interrupted on one side by the River Wensum, the city walls contained an area one-and-a-half miles north to south and one mile east to west. It is hard to believe that these strange heaps of rubble left over from the Middle Ages once stood at least 12ft high and were the pride of England’s second city.
More to read about the walls further down
Flint is a hard, tough chemical or biochemical *sedimentary rock that breaks with a conchoidal fracture. It is a form of microcrystalline quartz that is typically called “chert” by geologists. It often forms as nodules in sedimentary rocks such as chalk and marine limestones. The nodules can be dispersed randomly throughout the rock unit but are often concentrated in distinct layers. Some rock units form through the accumulation of silicious skeletal material. These can recrystallize to form a layer of bedded flint. Flint is highly resistant to weathering and is often found as pebbles or cobbles along streams and beaches.
Inside the nodule, flint is usually dark grey, black, green, white, or brown in colour, and often has a glassy or waxy appearance. A thin layer on the outside of the nodules is usually different in colour, typically white and rough in texture. From a petrological point of view, "flint" refers specifically to the form of **chert which occurs in chalk or marly limestone.
* Sedimentary rock facts:
Sedimentary rocks are formed by sediment that is deposited over time, usually as layers at the bottom of lakes and oceans. The sediment can include minerals, small pieces of plants and other organic matter. The sediment is compressed over a long period of time before consolidating into solid layers of rock. It forms layers called strata which can often be seen in exposed cliffs.
Sedimentary rocks cover the majority of the Earth's rocky surface but only make up a small percentage of the Earth’s crust compared to metamorphic and igneous types of rocks. Examples of sedimentary rocks include limestone, sandstone, mudstone, greywacke, chalk, coal, claystone and flint. Limestone forms the metamorphic rock marble when subjected to extreme heat and pressure over time (metamorphism). Sandstone forms the metamorphic rock quartzite. Mudstone forms the metamorphic rock slate. Chalk is a soft, white form of limestone. Flint is a hard, sedimentary form of the mineral quartz.
Three Types of Rock:
# Igneous (Volcanic)
# Metamorphic (Changed)
# Sedimentary (Layered)
** Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrouus sedimentary rock that may contain small fossils. It varies greatly in color (from white to black), but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements present in the rock, and both red and green are most often related to traces of iron (in its oxidized and reduced forms respectively).
Flint (chert) is a form of quartz, or silicon dioxide, also called silica. It occurs in layers and irregular nodules in the chalk and some other limestones. It is widely distributed around the world and was a primary material for stone age tools and weapons. Chemically, flint is complex. It is a fine mosaic of colloidal silica (opal) and crypto-crystalline silica (chalcedony).
Chalk beds were formed on the floor of ancient seas in the Cretaceous period between 145 million and 65 million years ago. Chalk is made up of individual crystals of calcium carbonate, from the bodies of microscopically small sea creature called Coccolithophores.
These formed a whitish mud which later solidified into limestone rock. Flint occurs both as layers and as irregular nodules in these chalk beds. There are extensive chalk deposits in the United Kingdom, France, Denmark, Poland, Russia, Ukraine, United States, Canada, and elsewhere. All contain flint.
Details of how the flint formed are still uncertain. The silica material is probably derived from the siliceous spicules of sponges and microscopic siliceous plankton, which are slightly soluble in water, so some of it dissolved in the ocean and was later precipitated out onto the chalk sea bed. Often it collected around some solid object such as a sponge or coral, and these are sometimes visible inside the flint when a nodule is broken open. It’s thought that initially, the silica must have gone through a gel-like phase before hardening into flint, because it is found completely filling shells such as those of sea urchins. Where flint nodules from the chalk have accumulated in superficial deposits, such as clay-with-flints, it is common to find internal casts in flint of the shells that were once filled. Flint nodules also formed in the cavities left in the sea floor by burrowing marine animals, hence their shapes.
Flint nodules in the chalk changed over time as their outside acquired a whitish-coloured cortex or rind, possibly through ground water percolating through the chalk. It’s thought the cortex formed because the flint surface is slightly more soluble in some microscopically small areas than in adjacent areas, so there is differential dissolving at the surface which results in a microscopic sponge-like structure. The cortex can be 5mm or more in thickness. When people started making tools from flint, they often removed the external cortex to get at the fresh flint inside, although in some cases they left a small amount of cortex to make some tools, such as scrapers and knives, easier to handle.
(A flint nodule weathering out of chalk beds.)
Various minerals can be included within the microscopically small cryptocrystalline structure of flint. Different mineral inclusions give rise to different colours. Freshly broken Flint is commonly black, grey, green, white or brown. The following semi-precious stones are all forms of quartz similar in structure to flint: Agate, Carnelian, Chalcedony, Jasper, Obsidian, Onyx and Opal. The microscopic structure of flint is capable of holding water molecules – as much as 30 per cent of the mass can be water, though it is typically 10 per cent. Some or all of this water may evaporate and leave the surface causing changes in colour and making the flint more brittle. Opal, for example, has a water content as high as 20 per cent, and often loses this water, and its rainbow colouration over time.
On the international hardness scale, flint ranks 7 out of 10, where diamond is 10, so it is harder than most materials commonly encountered in the natural environment. It also has the property of taking an edge thinner than a steel blade (only a few molecules thick) so it is literally sharper than a razor. Flint is still in use today as surgical tool because incisions made with a flint blade heal more quickly and are more sterile.
Flint does not have a regular crystal structure, like diamond, that would enable it to be cut into regular shapes like gemstones. Because of its cryptocrystalline structure, it shatters in a conchoidal or cone-shaped fracture, like glass. This property has a number of implications for someone wishing to make flint tools. When you strike a flint core with a hammerstone, you will always create a fracture cone spreading out from the point of impact. If you hit near the edge of the core, and at the right angle, the energy from your blow will strike off a flake. If you hit too far from the edge, or at the wrong angle, the energy from your strike will simply create a fracture cone inside the core. One or two mis-hits like that and your core becomes an unusable mass of intersecting fracture cones. Flint is thus very unforgiving to the inexperienced user. A second implication is that one cannot cut or carve flint at will as one can with most softer rocks – it can only be struck into flakes or blades in a specific chain of operations that makes use of its natural method of fracturing.
Where flints are buried in contact with the chalk, or with chalky soil, they tend to develop a white patina as in the flake shown above right. Third, where the implement lodges in ground containing iron minerals, the whitish patina absorbs the reddish or brownish ferrous material. And fourth, there can be an additional complex process in which molecules of quartz are dissolved from the surface and redeposited again forming a glossy coating of opal over the existing patina. This glossy coating or sheen is different from the gloss caused by wind abrasion in desert environments (desert gloss) and gloss caused by use wear (sickle gloss). There is a further patination feature associated with some flint tools and that is the occurrence of brownish spots mainly on the ridges between flake scars. This is known as ‘iron mould’, because its appearance resembles the spreading of a microorganism like mould.
It is common to find flints, both in worked form and as natural nodules, that have been calcined or heated by fire. Heating changes the appearance of flint to a grey, sometimes glossy surface, often cracked like the glaze on old pottery. In many cases, these calcined flints are associated with camp sites, and hence are believed to be hearth stones or ‘pot boilers’ – that is stones that have been heated in the fire and then placed in a container of water to boil it. Some experimental archaeologists think that people may have heated flint to some extent to make it easier to work, though this question is still debated.
Flint facts:
Flint occurs as lumps in chalk beds, in Europe and North America
It’s a form of quartz that is coloured by the inclusion of other minerals
Flint nodules from the chalk are coated with a thick whitish cortex
It has a cryptocrystalline structure - crystals so small they can't be seen in a microscope
When struck, flint fractures like glass
Flint is one of the hardest materials, close behind diamond
It takes a razor sharp edge, so is ideal for tools and weapons
Flint implements tend to weather in the ground – they can go white, brown or glossy
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Questions
1. Answer the questions under by visiting the Coordinates.
A. The coordinates given will lead you to a piece of the wall at Chapelfield where you will find a couple arrow loops. With a little re-search and check at gz. A1.Can you say anything on what is the dominant type of rock you find here? A2.Pick one and describe it in own words. A3. And why do you think this type of rock was used? (Answer can be found at GZ)
B. Feel the surface of the dominant rocks, what can you say about it? (Answer can be found at GZ)
C. What is the diameter and size of the average dominant rock used in the wall? And can you say anything about color of the rocks? (Answer can be found at GZ)
D. The part of the wall that you can see at gz, what would you estimate the height and thickness of it? And when the wall was raised, what was the height and thickness then? (Answer can be found in text and at GZ)
E. What is the dominant rock most known used as? (For millions of years ago)? And why? (Answer can be found in text.)
2. Take a photo of yourself, the group or your GPS when logging the cache. Without revealing any answers! (It’s voluntary to post a photo in your online log)
Norwich - The City Wall
The medieval city of Norwich was defended on its north, west and south sides by a high, flint wall and was enclosed by a deep and wide defensive outer ditch in 1252. Brick and stone were used for strengthening the angles of the flint walls and for features such as doorways, arrow loops and crenellations. Evidence indicates the flint wall was begun around 1294 and was completed by the middle of the 14th century. The defenses of the city were maintained and occasionally modified until the late 18th century. At night the walls were shut, providing security for the citizens. On the east side of the city, although there was no wall because this side was protected by the river, the Bishop's Bridge was defended by a gatehouse. There were towers at regular intervals along the wall, linked by a wall walk, and there were eleven substantial gateways built across each of the main streets leading into the city. The heads of those executed at the city gallows were displayed on the gates of the city walls. Most of the gateways were demolished in 1793/4 and the last gate to survive was at Magdalen Street, which was removed in 1808. Over time, much of the walls have also disappeared. Buildings gradually encroached on it and sections collapsed or were plundered for building materials. Parts were demolished for redevelopment and road widening.
Today, 15 sections survive above ground. These include Cow Tower and the towers at Carrow Hill.
If you follow the link, you will be guided to a google overview of the remaining city wall.
1) You can also have a look at the map at this link.
2) You can also have a look at the map at this link.
Much more history info on the wall and year before, under and after can be found at the link under:
General conclusions:
Some general observations can be made about the character of the surviving wall.
Only at Ber Street, to the east of the site of the gate, does the wall survive to its full height including the parapet wall of the wall walk with merlons and crenellations. From this section it is possible to get some sense of the scale of the wall, here almost 7 metres high, though even here what has been lost is the effect of seeing the wall rise up from the far side of a wide and deep ditch. The walls must originally have presented an impressive if not ominous view from inside the city as well as out, looming over all domestic buildings and dominating the view along all the streets that led up to the gates.
The wall was at least 1.9 metres thick though it is not always possible to determine the full width from the standing sections where extensive areas of facing flint were lost when buildings added against the wall were demolished. The full thickness of the wall has only been revealed when sections have been excavated. The wall through Jarrold's factory at River Lane is thin and completely rebuilt above ground. Excavations by the County Archaeologist revealed that because the outer ditch here was particularly wide and deep where it joined the river, the original wall, surviving below the present ground level, was very substantial.
The wide wall allowed for a wall walk at the top protected by a thinner parapet on the outer side. Where this parapet survives at Carrow Hill it rises about 2 metres above the walk, providing full cover for men keeping watch or defending the city from the wall top.
In 1294 the City Walls was begun. Although they were said to be completed in 1320, it is Richard Spynk who has alway been credited with finishing the job and supplying the gates and towers with "warlike instruments" in 1341 for great service a grateful City quitted him and his decendants of taxes and tolls "for ever" . By 1809 the last city gate was demolished and today the names of the gates still live on, there were twelve gates that gave access to the City.
They were:
1- King St (South Gate),
2- Ber St Gates ( one of the first to be erected. In the 1726 it was taken down - on the side of the Ber Gates public house on the gable end is a mural of the gate),
3- Brazen Doors or New Gates,
4- St. Stephens Gates ( known as the Nedeham Gate) Because of its situation, this was the principal gate and the one from which Elizabeth 1 entered.
5- St. Giles Gate falling into decay, this gate was taken down in 1792,
6- St. Benedicts Gates or Westwick Gates another casualty of 1793, and on the north side of the river,
7- St. Martins Gate or Coslany Gates it was taken down in 1808,
8- St. Augustine's Gates demolished in 1794,
9- Magdalen Gates Anciently called Fye
10- Bridge Gate demolished in 1808 and was said to be the last gate to go,
11- Pockthorpe Gate or Bar gates the name means Little Thorpe,
12- Bishop's Gates not to be confused with Bishopgate (where gate means way) the gates were built and maintained by the Bishops of Norwich till 1393 when the city took over ownership.
Today there still remains some fine examples of the old City Walls. For the visitor a walk along Chapelfield towards St. Stephens near to the new Chapelfield shopping complex where you can see evidence of arrow loops. Arriving at the roundabout take a right turn and discover the Coach and Horses Public House on the wall above is a very attractive mural of the St. Stephens Gate (known at the Nedeham Gate) in 1320. Cross the road by the subway and take the bus station exit you will continue to see fine examples of the old City Walls, these walls were almost lost in 1970 when the Norwich City Council debated on the old walls being demolished they were only saved by the Chairmans vote.
Remains can also be seen at Carrow Road, the junction of Magpie Road and Magdalen Street where the gate once stood and at Barrack Street. At St Stephens a fine mural illustrates the gate in its glory days. There have been a few archaeological digs, most notably during the 1950s at Barn Road, but the walls retain much of their air of mystery.
