Saturday, 26 May 2018
Friday, 25 May 2018
We are lucky to have birds!
The K-Pg Event Almost Killed the Birds
In this article a researcher from Bath University says that only a small number of ancestral bird species survived the asteroid impact that did for the dinosaurs.
All the tree living ones died; probably because all the trees were destroyed! Only five bird lineages survived and they were all ground dwellers. There is a lot more in the original paper, but this is far from my (limited) areas of expertise so I will leave criticism of the evidence to others.
 |
| The tinamous is one of the most similar living birds to those that survived the K-Pg. Daniel J Field, Author provided |
Saturday, 19 May 2018
21st to 27th May 2018
NEXT WEEKS EVENTS
21st TO 27TH MAY 2018
THE FOLLOWING IS AN EXTRACT FROM BRISTOL AND WEST COUNTRY GEOLOGY CALENDARS
MORE DETAILS CAN BE FOUND IN THE BRISTOL AND THE WEST COUNTRY CALENDARS AND ON THE WEB SITES OF THE RELEVANT SOCIETY OR ORGANISATION.
MONDAY 21st
Dave Green - Planetary Geology
When
Mon, 21 May, 19:30 – 21:30
Description
Planetary Geology. Monday 16th April, for 10 weeks, until 9th July (not 7th nor 28th May). The state of knowledge of the planets of the solar system has improved vastly in the past 40 years as a result of space missions and improved technology for observation and analysis. The course will examine the results of this activity and evidence for these interpretations in terms of the internal structure, magnetism and geophysics of these bodies; their tectonics and volcanism, the effects of impacting bodies, and the surface conditions –atmospheres, oceans, sedimentary features and biology. Held at Wynstones School, Stroud Road, Whaddon, Gloucester from 7.30-9.30pm on Mondays. Cost £70.
Dave Green, Joys Green Farm, Forge Hill, Lydbrook, Glos GL17 9QU Tel 01594 860858
Tuesday 22nd
Wednesday 23rd
Lecture - Quarrying Bath Stone
When
Wed, 23 May, 19:30 – 21:00
Where
Bath Royal Literary & Scientific Institution, 16-18 Queen Square, Bath BA1 2HN, UK (map)
Description
See Details HERE
Thursday 24th
Friday 25th
Dave Green, Field Course: The Geology of Western Norway
When
25 May – 4 Jun 2018
Where
Western Norway (map)
Description
Field Course: The Geology of Western Norway Dates will be for a week to 10 days around a period from May 25th to June 4th. At this stage I envisage a two, or three base trip, including the Nordfjord, Trondhjeim and Lofoten areas, to study basement of Archaean and Proterozoic age, the trans-Scandinavian intrusive belt, Caledonian nappes, mineralisation and of course, glaciers and the fantastic fjord scenery.
Dave Green, Joys Green Farm, Forge Hill, Lydbrook, Glos GL17 9QU Tel 01594 860858
Saturday 26th
OUGS Severnside - Field Meeting
When
26 – 27 May 2018
Description
North Wales Weekend
Leader: Tom Cotterell
Date: May 26th–27th, 2018
Type: Weekend Trip
Summary: A trip to examine the minerals of North Wales, led by the senior curator of mineralogy at the National Museum of Wales.
Click here for contact info and additional details
Sunday 27th
Dave Green - Planetary Geology
When
Mon, 21 May, 19:30 – 21:30
Description
Planetary Geology. Monday 16th April, for 10 weeks, until 9th July (not 7th nor 28th May). The state of knowledge of the planets of the solar system has improved vastly in the past 40 years as a result of space missions and improved technology for observation and analysis. The course will examine the results of this activity and evidence for these interpretations in terms of the internal structure, magnetism and geophysics of these bodies; their tectonics and volcanism, the effects of impacting bodies, and the surface conditions –atmospheres, oceans, sedimentary features and biology. Held at Wynstones School, Stroud Road, Whaddon, Gloucester from 7.30-9.30pm on Mondays. Cost £70.
Dave Green, Joys Green Farm, Forge Hill, Lydbrook, Glos GL17 9QU Tel 01594 860858
Lecture - Quarrying Bath Stone
When
Wed, 23 May, 19:30 – 21:00
Where
Bath Royal Literary & Scientific Institution, 16-18 Queen Square, Bath BA1 2HN, UK (map)
Description
See Details HERE
Dave Green, Field Course: The Geology of Western Norway
When
25 May – 4 Jun 2018
Where
Western Norway (map)
Description
Field Course: The Geology of Western Norway Dates will be for a week to 10 days around a period from May 25th to June 4th. At this stage I envisage a two, or three base trip, including the Nordfjord, Trondhjeim and Lofoten areas, to study basement of Archaean and Proterozoic age, the trans-Scandinavian intrusive belt, Caledonian nappes, mineralisation and of course, glaciers and the fantastic fjord scenery.
Dave Green, Joys Green Farm, Forge Hill, Lydbrook, Glos GL17 9QU Tel 01594 860858
OUGS Severnside - Field Meeting
When
26 – 27 May 2018
Description
North Wales Weekend
Leader: Tom Cotterell
Date: May 26th–27th, 2018
Type: Weekend Trip
Summary: A trip to examine the minerals of North Wales, led by the senior curator of mineralogy at the National Museum of Wales.
Click here for contact info and additional details
Thursday, 17 May 2018
Down to Earth Extra - June
Down to Earth Extra - June
You can get the latest Down to Earth Extra HERE.
Or you can read it on this page.
Wednesday, 16 May 2018
Archaeopteryx yet again
Archaeopteryx Studies (Continued)
The question on everyone's lips - "was Archaeopteryx capable of flying" - has been answered positively; at least to the satisfaction of the authors of THIS PAPER.
More accessible versions can be found HERE and HERE. Because Archaeopteryx fossils are so precious, non-destructive methods have to be used and the latest is the European synchroton in Grenoble. There, researchers found Archaeopteryx bones most resembled those of pheasants - birds that occasionally use active flight to cross barriers or dodge predators.
There is a lot more about it in the papers, especially the Nature one. I will leave you to read them all at your leisure.
Tuesday, 15 May 2018
Information on Kilauea eruptions
Information on Kilauea eruptions
Information can be difficult to get about the current volcanic activity on the Big Island in Hawaii. THIS ARTICLE has a good introduction to the activity and has lots of links to a multitude of information. I especially liked THIS one. Click on the photos to get the BIG picture!
Healing crystals
Tempted to get "Healing Crystals"? - Read This
I got my geology degree from Aberdeen when Professor T. C. Phemister was in charge and therefore I had four years of mineralogy and crystallography.
I don't think the health giving properties of crystals were mentioned once.
We were told to keep the asbestos in its glass box and not to lick our fingers when we were looking at arsenic. Not a great deal more on the health front.
But now you are probably aware that many crystalline substances are sold for their healing properties. HOW they heal is never mentioned.
I you are tempted to buy, read this article first. It discusses the ecological damage their mining causes and also the exploitation of miners and child miners. This does not appear on the sales pitch.
There are many good reasons to look at crystals. I don't think health is high on the list.
 |
| A miner holding an amethyst crystal in Ametista do Sul, Brazil. Photo by Caio Guatelli. |
Rockwatch programme
Rockwatch Programme, Summer 2018
Here is the Rockwatch Programme for this summer. Several of them are in our area and these have been entered in the calendars - HERE and HERE.
Rockwatch Fieldtrips coming up. All of them can be booked through the website: www.rockwatch.org.uk
Etches Collection Museum and Kimmeridge field trip, Dorset BH20 5PE
Saturday 16 June
Private tour and workshop at this new immersive museum of locally found fossils plus a beach visit giving you an opportunity to find your own fossils! Go back to a time before humans existed, before our planet was formed as we know it today and a time when parts of Dorset were under the sea. Visit the Exhibition Gallery and experience a laboratory of the senses as you are taken on an immersive journey through life underwater in the tropical seas of Kimmeridge 150 million years ago, surrounded by wonderful, if not weird creatures, some of which have long vanished from the face of our Earth. Book through the website
‘Changing times, changing environments’ - Explore the Yorkshire Coast with Paul Hildreth, Mick Oates and Susan Brown on Sunday 24 June. 10.30 -4.30
A visit two geological sites - Burniston Wyke on the coast in the morning and Betton Farm, an inland site and of younger age rocks, in the afternoon. The Jurassic rocks at Burniston represent an environment of forested delta flats and meandering river channels where giant reptiles roamed and we hope to find evidence of these. We’ll also show you how to calculate the size of the animals. At Betton Farm Quarry we’ll see younger Jurassic rocks and look for evidence of their depositional environment, different from those at Burniston Wyke. At Betton we’ll see evidence of warm tropical seas and coral reefs with their fossil assemblages. Book through the website. Age 7+
South Wales Annual Weekend in Pembrokeshire Saturday 14 – Sunday 15 July
This year we will be exploring the stunning Pembrokeshire coast. We will be investigating the spectacular geology, scenery and building stones of the St David’s Peninsula which includes sedimentary and igneous rocks (Precambrian – Ordovician) and Quaternary landforms and deposits which give an important insight into ‘climate change’. There will be walks along the local coastal footpath as far as Porthliskey and a look at the north coast of the peninsula. Suitable for 10 year olds and above as there is a fair amount of walking to do! Book through the website
Rockwatch fieldtrip to the Island of Eigg (NOW FULLY BOOKED BUT YOU CAN GO ON THE WAITING LIST)23rd – 27th July (10.15 ferry from Mallaig so you must be there for night of 22nd)
A fabulous opportunity to explore Eigg with its interesting sedimentary and volcanic rocks. Beneath the volcanic rocks are older sedimentary rocks from the Jurassic Period with plenty of fossils including shells and plant remains. Plesiosaur bones were discovered, by a famous geologist called Hugh Miller in 1844, and if you go to the right place it is still possible to find bits of plesiosaur today. This trip involves 4 nights on Eigg, where we have taken over Glebe Barn hostel and 1 night near the ferry which you must book yourself. The trip is flexible and informal, so time to explore all of the island, spend time on beautiful sandy beaches and climb An Sgùrr. Further info about Eigg is available at www.isleofeigg.org. The cost of the trip is yet to be confirmed but email if you are interested to hello@rockwatch.org.uk Places limited. Over 7s only
16th Annual Rockwatch Residential Fieldtrip – to the Jurassic World Heritage coast of Dorset and East Devon Monday 30 July – Friday 3 August
Join the team with Susan, Aerona, Alan, Sam, Simon, Richard and Mike for a week exploring quarries on the Isles of Purbeck and Portland. Hear about the smugglers’ tales along these cliffs and see where they hid their booty! Explore beaches and cliff tops, find fossils and dinosaur footprints and maybe do some rock carving and find a few caves to explore along the way. You’ll be investigating the geology of Weymouth and going over to Portland where you can see extraordinary sweep of Chesil Beach – and possibly finding some dinosaur footprints!
Your accommodation during the week will be the Leeson House Field Study Centre in Langton Maltravers outside Swanage which is comfortable, spacious and with grounds to have a run around. The cost of the trip includes all your food during the stay and transport during the whole visit. If you arrive by train you will be met at the station – luxury!
Adults (aged from 18 up): £320.00
First child (up to 17 years inclusive): £225.00
Second child: £145.00
If you would like to go on this residential fieldtrip either email the Rockwatch office: hello@rockwatch.org.uk and ask for a booking form or book a place on line.
www.rockwatc.org.uk (I think they mean www.rockwatch.org.uk)
Ware Museum, The Priory, High St, Ware, Hertfordshire SG12 9AL
Tuesday 14 August 11.00 – 3.00 - www.waremuseum.org.uk 01920 487848
Rockwatch will be joining a ‘drop in’ activities day at this delightful local museum. Come along and make a Jurassic diorama, handle fossils, paint plaster fossils – bring your own rocks and fossils to be identified and have a go at other geo-crafts! Free event for Rockwatch members. £2.50 per individual for non members. No booking required.
Explore the Runswick Bay on the Yorkshire CoastTuesday 28 August 11.00 – 4.00
Rockwatch is joining Will Watts and the Hidden Horizons team for a fossil hunting trip along Runswick Bay. You should be able to find a wide range of fossils from the Jurassic, around 160 million years ago. Suitable for all the family as the access is very easy. Booking essential through www.hiddenhorizons.eventbrite.co.uk Use the promotional code ‘Rockwatch’ on 28 August trip to unlock the special price of £2.50 ticket. All under 16s must be accompanied by an adult.
Saturday, 12 May 2018
14th to 20th May 2018
NEXT WEEKS EVENTS
14th to 20th May 2018
THE FOLLOWING IS AN EXTRACT FROM BRISTOL AND WEST COUNTRY GEOLOGY CALENDARS
MORE DETAILS CAN BE FOUND IN THE BRISTOL AND THE WEST COUNTRY CALENDARS AND ON THE WEB SITES OF THE RELEVANT SOCIETY OR ORGANISATION.
MONDAY 14TH
19:30
Dave Green - Planetary Geology
When
Mon, 14 May, 19:30 – 21:30
Description
Planetary Geology. Monday 16th April, for 10 weeks, until 9th July (not 7th nor 28th May). The state of knowledge of the planets of the solar system has improved vastly in the past 40 years as a result of space missions and improved technology for observation and analysis. The course will examine the results of this activity and evidence for these interpretations in terms of the internal structure, magnetism and geophysics of these bodies; their tectonics and volcanism, the effects of impacting bodies, and the surface conditions –atmospheres, oceans, sedimentary features and biology. Held at Wynstones School, Stroud Road, Whaddon, Gloucester from 7.30-9.30pm on Mondays. Cost £70.
Dave Green, Joys Green Farm, Forge Hill, Lydbrook, Glos GL17 9QU Tel 01594 860858
davegeostudies@gmail.com
TUESDAY 15TH
WEDNESDAY 16TH
Thursday 17Th
19:00
Thornbury Geology Group, 7.30pm, The Chantry, Thornbury
When
Thu, 17 May, 19:00 – 21:30
Description
Thornbury Geology Group, 7.30pm at The Chantry, Thornbury, and every 3rd Thursday in the month.
Friday 18th
Saturday 19th
Sunday 20th
South Wales GA - Field Meeting
When
Sunday, 20 May 2018
Description
The Tortworth Inlier, Gloucestershire. (Dave Green)
19:30
Dave Green - Planetary Geology
When
Mon, 14 May, 19:30 – 21:30
Description
Planetary Geology. Monday 16th April, for 10 weeks, until 9th July (not 7th nor 28th May). The state of knowledge of the planets of the solar system has improved vastly in the past 40 years as a result of space missions and improved technology for observation and analysis. The course will examine the results of this activity and evidence for these interpretations in terms of the internal structure, magnetism and geophysics of these bodies; their tectonics and volcanism, the effects of impacting bodies, and the surface conditions –atmospheres, oceans, sedimentary features and biology. Held at Wynstones School, Stroud Road, Whaddon, Gloucester from 7.30-9.30pm on Mondays. Cost £70.
Dave Green, Joys Green Farm, Forge Hill, Lydbrook, Glos GL17 9QU Tel 01594 860858
davegeostudies@gmail.com
19:00
Thornbury Geology Group, 7.30pm, The Chantry, Thornbury
When
Thu, 17 May, 19:00 – 21:30
Description
Thornbury Geology Group, 7.30pm at The Chantry, Thornbury, and every 3rd Thursday in the month.
South Wales GA - Field Meeting
When
Sunday, 20 May 2018
Description
The Tortworth Inlier, Gloucestershire. (Dave Green)
Landslide Mobility!
Video Demonstrating Landslide Mobility
I came across this web page and found it very interesting. Especially the accompanying video which you can see if you click the link. Its on Facebook and I cannot find a way of embedding it in the blog.
But well worth looking at.
But well worth looking at.
Monday, 7 May 2018
Bath Lecture
Lecture About Quarrying Bath Stone
A source put this on Facebook and it looks rather interesting.
Can you find up?
Geological Skills Test - Which way is UP?
HERE is a test for you! Don't scroll down the page until you have reached your decision.
Click on the "Fullscreen" button (the two diverging arrows) on the black band at the top of the photo and it will become full screen and you can zoom in and out with the + and - at the bottom right, or use your mouses scroll wheel. Press "Escape" to return to the previous page.
Your task is to decide if the rock sample is younging to the left or right.
Once you have decided, return to the previous page and scroll down to find teachers answer. And you can go fullscreen to check whether you agree with teacher!
Saturday, 5 May 2018
7th to 13th May 2018
NEXT WEEKS EVENTS
7tH TO 13TH MAY 2018
THE FOLLOWING IS AN EXTRACT FROM BRISTOL AND WEST COUNTRY GEOLOGY CALENDARS
MORE DETAILS CAN BE FOUND IN THE BRISTOL AND THE WEST COUNTRY CALENDARS AND ON THE WEB SITES OF THE RELEVANT SOCIETY OR ORGANISATION.
MONDAY 7TH
Tuesday 8th
Wednesday 9th
Celestine Mining in South Gloucestershire
When
Wed, 9 May, 19:30 – 21:00
Where
Room 2Q50/51, Faculty of Environment & Technology University of West of England, Frenchay Campus, Bristol BS16 1QY (map)
Description
Synopsis: Celestine (Strontium Sulphate) is a crystalline evaporite mineral that although having few uses in itself has historically been the main source of strontium for producing other more useful minerals. For over 100 years nearly all of the global extraction of this mineral came from a small area north of Bristol UK. This talk looks at the early history of the mineral from its discovery and identification, through its early uses, to the commercial working of the mineral in this country until it finally ceased in the 1990s.
Directions: The University is easy to reach being situated close to the M4 and M5 motorways. There are also
excellent train and coach connections. See also http://www1.uwe.ac.uk/about/visitus/howtofindus.aspx
Parking: Use the North Entrance to access car parks. The “Visitor Parkin” is the nearest to Q block and is
free after 5:00pm (NB - Use BS34 8QZ for your sat nav).
Full details HERE
Thursday 10th
GeoWeek - Tour of Batts Combe Quarry
When
Thu, 10 May, 10:00 – 12:00
Where
Meet at Batts Combe Quarry office car park, Warrens Hill, Cheddar (map)
Description
Free Events in the Mendips for Geo Week 2018
Event name Batts Combe Quarry Tour - a Limestone Legacy
Event activity details
Join the Mendip Rocks team and Hanson UK for an extensive tour of
an operating Mendip Limestone Quarry. This quarry is noted for its
purer Burrington Oolite Limestones, which has industrial uses such
as agriculture, animal feeds and industrial fillers. Most of the tour will
be by minibus, with a small amount of walking on uneven ground.
Tour will be for two hours - 10am until 12noon, covering quarry
operations and geology of the quarry. Safety gear provided on site.
Meet at Batts Combe Quarry office car park, Warrens Hill, Cheddar.
Must wear wellies or walking boots/long sleeves, no shorts.
Booking Essential as limited places: call Dr Gill Odolphie on
01749 840156 or gill@earthsciencecentre.org.uk
Event details Free, Walking boots & wet weather gear, Uneven surfaces/public footpaths
Date Thursday 10 May 2018
Start time 10:00 am – 12 noon
Type of event Guided Field Trip
Friday 11th
Saturday 12th
Sunday 13th
OU Geol Soc Wessex - Excursion
When
Sunday, 13 May 2018
Where
Durdle Cove, Dorset (map)
Description
The Chalk of Durdle Cove, Dorset
'THE' Chalk expert will be explaining the geology of Durdle Cove with an emphasis on the chalk.
Professor Rory Mortimore is a well known figure in the geological world of chalk. We are lucky to have such an eminent figure to lead one of our trips again. This is not to be missed.
Contact Jeremy Cranmer
wessexdaytrips@ougs.org
tel. 01305 267133
---------------------------------
GeoWeek - Mendip Mountain building
When
Sun, 13 May, 14:00 – 16:00
Where
Meet at 2.00 pm at Deer Leap car park (ST 5190 4927; BA5 1EL) (map)
Description
Mendip mountain building on your doorstep –The Deer Leap/EbborGorge Experience
Join Doug Robinson and Chris King to explore the remarkable geological and historical stories of the Mendip Deer Leap/Ebor Gorge area. It is a story of idyllic tropical seas that were eventually invaded by large river deltas. Then, when the area lay astride the equator, enormous forces bent and broke these rocks to form the Mendip mountains. How warm were the seas? What caused the mountain building and how high were the mountains? We will not only discuss these questions, but will also ask, did the makers of the standing stones, the mediaeval farmers and the local coal miners in the 1800s really know what they were doing?
Meet at 2.00 pm at Deer Leap car park (ST 5190 4927; BA5 1EL) We need to limit numbers for safety reasons, so please email Chris to book a place .
Booking Essential: chrisjhking36@gmail.com.
Event details Free, Walking boots & wet weather gear, Uneven surfaces/public footpaths
Date Sunday 13 May 2018 2:00 p.m.
Start time 14:00 – 17.00
Type of event Guided Field Trip
When
Wed, 9 May, 19:30 – 21:00
Where
Room 2Q50/51, Faculty of Environment & Technology University of West of England, Frenchay Campus, Bristol BS16 1QY (map)
Description
Synopsis: Celestine (Strontium Sulphate) is a crystalline evaporite mineral that although having few uses in itself has historically been the main source of strontium for producing other more useful minerals. For over 100 years nearly all of the global extraction of this mineral came from a small area north of Bristol UK. This talk looks at the early history of the mineral from its discovery and identification, through its early uses, to the commercial working of the mineral in this country until it finally ceased in the 1990s.
Directions: The University is easy to reach being situated close to the M4 and M5 motorways. There are also
excellent train and coach connections. See also http://www1.uwe.ac.uk/about/visitus/howtofindus.aspx
Parking: Use the North Entrance to access car parks. The “Visitor Parkin” is the nearest to Q block and is
free after 5:00pm (NB - Use BS34 8QZ for your sat nav).
Full details HERE
GeoWeek - Tour of Batts Combe Quarry
When
Thu, 10 May, 10:00 – 12:00
Where
Meet at Batts Combe Quarry office car park, Warrens Hill, Cheddar (map)
Description
Free Events in the Mendips for Geo Week 2018
Event name Batts Combe Quarry Tour - a Limestone Legacy
Event activity details
Join the Mendip Rocks team and Hanson UK for an extensive tour of
an operating Mendip Limestone Quarry. This quarry is noted for its
purer Burrington Oolite Limestones, which has industrial uses such
as agriculture, animal feeds and industrial fillers. Most of the tour will
be by minibus, with a small amount of walking on uneven ground.
Tour will be for two hours - 10am until 12noon, covering quarry
operations and geology of the quarry. Safety gear provided on site.
Meet at Batts Combe Quarry office car park, Warrens Hill, Cheddar.
Must wear wellies or walking boots/long sleeves, no shorts.
Booking Essential as limited places: call Dr Gill Odolphie on
01749 840156 or gill@earthsciencecentre.org.uk
Event details Free, Walking boots & wet weather gear, Uneven surfaces/public footpaths
Date Thursday 10 May 2018
Start time 10:00 am – 12 noon
Type of event Guided Field Trip
OU Geol Soc Wessex - Excursion
When
Sunday, 13 May 2018
Where
Durdle Cove, Dorset (map)
Description
The Chalk of Durdle Cove, Dorset
'THE' Chalk expert will be explaining the geology of Durdle Cove with an emphasis on the chalk.
Professor Rory Mortimore is a well known figure in the geological world of chalk. We are lucky to have such an eminent figure to lead one of our trips again. This is not to be missed.
Contact Jeremy Cranmer
wessexdaytrips@ougs.org
tel. 01305 267133
---------------------------------
GeoWeek - Mendip Mountain building
When
Sun, 13 May, 14:00 – 16:00
Where
Meet at 2.00 pm at Deer Leap car park (ST 5190 4927; BA5 1EL) (map)
Description
Mendip mountain building on your doorstep –The Deer Leap/EbborGorge Experience
Join Doug Robinson and Chris King to explore the remarkable geological and historical stories of the Mendip Deer Leap/Ebor Gorge area. It is a story of idyllic tropical seas that were eventually invaded by large river deltas. Then, when the area lay astride the equator, enormous forces bent and broke these rocks to form the Mendip mountains. How warm were the seas? What caused the mountain building and how high were the mountains? We will not only discuss these questions, but will also ask, did the makers of the standing stones, the mediaeval farmers and the local coal miners in the 1800s really know what they were doing?
Meet at 2.00 pm at Deer Leap car park (ST 5190 4927; BA5 1EL) We need to limit numbers for safety reasons, so please email Chris to book a place .
Booking Essential: chrisjhking36@gmail.com.
Event details Free, Walking boots & wet weather gear, Uneven surfaces/public footpaths
Date Sunday 13 May 2018 2:00 p.m.
Start time 14:00 – 17.00
Type of event Guided Field Trip
The Geological Column
An Essay on the Geological Column
This article discusses the geological column and is a useful and well written appraisal of the column. It mentions some of the many changes that have been made and the means used to determine where the boundaries are. Well worth reading!
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