Friday, 17 January 2020

Is Venus Active? (Volcanically)

Is Venus Active? (Volcanically)

Not much is known about Earth's nearest planetary neighbour, Venus. It has a reflective cloud cover,over a 96% CO2 atmosphere, which leads to surface temperatures of about 500oC. A few Russian missions to the planet survived long enough to determine that the surface rock was of basaltic composition.

The atmosphere is transparent to radar waves and it is found to be a flat place with few impact craters but many volcanic craters.

Volcanic ‘pancake’ domes on the surface of Venus, about 65 km wide and 1 km high, imaged by orbital radar carried by NASA’s Magellan Mission.

THIS ARTICLE describes an ingenious method of determining if Venus is currently (or recently) active volcanically. In laboratory experiments they determined what would happen to olivine in Venus's atmosphere. Fresh olivine emits more radiation than olivine tarnished in Venus's atmosphere.

A carbon dioxide atmosphere does let some radiation through at a few spectral windows; windows in which olivine emits its radiation. Using this we can see "hot spots" which indicate fresh olivine - and given Venus's atmosphere, olivine does not stay fresh for long!

Colour-coded image of night-time thermal emissivity over Venus’s southern hemisphere as sensed by VIRTIS on Venus Express (Credit: M. Gilmore 2017, Space Sci. Rev. DOI 10.1007/s11214-017-0370-8; Fig. 3)

So, does Venus have active volcanoes - very possibly!

Saturday, 11 January 2020

13th to 19th January 2019


NEXT WEEKS EVENTS

13th to 19th January 2019


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 13TH

Geostudies Lecture Course - Germany
Monday, 13 January⋅19:30 – 21:30
Weekly on Monday, until 29 Mar 2020
Wynstones School, Stroud Road, Whaddon, Gloucester
Description:The Geology of Germany 

 Monday 13th for 10 weeks (not 17th Feb) until 23rd  March. Held at Wynstones School, Stroud Road, Whaddon, Gloucester from 7.30 - 9.30pm on Mondays. 

Like Britain, Germany consists of a number of exotic Terranes, derived from different continents and amalgamated together by plate tectonic collisions. Northern Germany is part of Avalonia, which amalgamated with the East European Craton (Baltica) along the Tornquist suture in the east. A great deal of this area is plastered by thick Quaternary glacial sediments. 

Central Germany is part of Armorica, which collided with the north during the Variscan orogeny. There is, in places, thick Mesozoic unconformable cover. The extreme south is part of the Alpine orogeny, but its effects were transmitted northwards to affect and reactivate older structures. There was extensive volcanic activity during the Tertiary, and some famous asteroid impact sites. 

Cost £75

TUESDAY 14TH

Cardiff University Lecture - Volcanoes—all you need to know!
When
Tue, 14 January, 18:30 – 20:00
Where
School of Earth and Ocean Sciences will be held in the Wallace Lecture Theatre (0.13), Main Building, Cardiff University, Park Place, Cardiff CF10 3AT (map)
Description
Volcanoes: from fuming vents to extinction events. Tamsin Mather, Earth Sciences, Oxford

The 2019-2020 monthly Tuesday evening lecture series in the School of Earth and Ocean Sciences will be held in the Wallace Lecture Theatre (0.13), Main Building, Cardiff University, Park Place,
 Cardiff CF10 3AT.  Lectures begin at 18.30.  Booking is not needed.  Should you require the Q&A sessions to be in Welsh, please email edwardsd2@cardiff.ac.uk at least two weeks before the event.

Did you know that the majority of volcanic eruptions – maybe even 90% – occur under water and of which we are largely unaware? There remains a very great deal we don't know about volcanoes, but many exciting new insights are emerging from ongoing research. This lecture series will encompass the diversity of volcanoes, their functioning and products, together with the nature of eruptions and their attendant problems of predictions plus their ensuing past and present environmental and biological impacts.

WEDNESDAY 15TH



THURSDAY 16TH

Geostudies Lecture - Uniformitarianism
When
Thu, 16 January, 19:30 – 21:30
Where
The Chantry, Thornbury (map)
Description

The Limits of Uniformitarianism.


The science of geology is heavily dependent on the principle of uniformitarianism – the idea  that geological conditions and processes have remained substantially unchanged through geological time, meaning that we can interpret the past on the basis of our understanding of the geological present. But how accurate is this principle? To what extent were conditions and processes different in the past? Are present conditions and processes typical? How well do we understand present processes? And there are also spatial features to consider; A casual examination of a modern sedimentary or volcanic environment reveals rapid and wide-ranging changes in facies over a small area. Our evidence of past environments is largely based on small, possibly unrepresentative, exposures of tiny fractions of those past environments. Are we justified in using evidence from the past to interpret the present and future, such as climate change?  Held at The Chantry, Thornbury, in the Hanover Room.  First meeting 7.30 – 9.30, Thurs 16th  January until April 2nd  (not Thurs 20th Feb or 19th March). Cost £75


Programme

What do we mean by Uniformitarianism? Origin of the term and the historical context in which it arose and developed as a counter to “Old” Catastrophism.

What are the main problems with Uniformitarianism? The rise of “New” Catastrophism in the later part of the 20th century. Problems of direction, cyclicity, punctuation, gradualism in the following fields of geology:

Uniformitarianism and sedimentation. Have conditions changed over geological time? How representative in terms of coverage and completeness is the sedimentary record?

Uniformitarianism and volcanicity, earthquakes, intrusion and landslides

Uniformitarianism and the solar system – external processes affecting earth geology

Uniformitarianism and major environmental change (such as climate and sea level changes)

Uniformitarianism, evolution and mass extinction  

Uniformitarianism and tectonics – was plate tectonics a relatively young development? Is the Wilson (supercontinent) Cycle real?

Geomorphology and Uniformitarianism

Is the present the key to the past? (or in reverse?)


Useful Reading

There is very little in the form of recently published books on the subject, though there are some classic older publications, not issued as e-books:

Berggren and Van Couvering Catastrophism and Earth History – the new uniformitarianism (1984)

C C Albritton Catastrophic Episodes in Earth History (1989)

D V Ager The Nature of the Stratigraphic Record (1993 3rd edition) 

DV Ager The New Catastrophism (1993)

Tony Hallam Catastrophes and Lesser Calamities – the causes of mass extinctions (1994)

Richard Huggett Catastrophism (1997 2nd edition)  

FRIDAY 17TH



SATURDAY 18TH



sunday 19th



Thursday, 9 January 2020

Blobs in the Mantle

Blobs in the Mantle

There are blobs in the mantle. Are they hotter areas or are they a different composition?



Two enormous regions of ultra-hot material sit beneath Africa and the Pacific Ocean.
Olena Shmahalo/Quanta Magazine; source data: Sanne Cottaar


A correspondent has brought THIS ARTICLE to my attention. It discusses the possibilities and describes how they were found. And this gives them their name - Large Low-Shear-Velocity Provinces or LLSVPs. 

The different composition theory seems to be winning at the moment. But is the composition difference due to crystal settling during cooling or are they parts of Theia, the Mars sized body whose impact with the Earth gave rise to the Moon?

Obviously there is a lot still to be settled about these blobs including the affect they have on the Earths surface. Read the article to get some idea of how little we know!

Saturday, 4 January 2020

6th to 12th January 2020


NEXT WEEKS EVENTS

6th to 12th January 2020


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 6TH



Tuesday 7th



wednesday 8th



thursday 6th



Friday 7th



saturday 8th

South Wales G A - Lecture
When
Saturday, 11 Jan 2020
Where
Venue to be confirmed (map)
Description
Holiday Geology
--------------------------------

DGAG AGM
When
Sat, 11 January, 14:00 – 17:00
Where
Broadmayne Village Hall, Cowleaze Rd, Broadmayne, Dorchester, Dorset, DT2 8EW (map)
Description
Saturday January 11th: DGAG AGM, Broadmayne Village Hall. 2 p.m.-5 p.m. 


sunday 9th




Fertilising the oceans with iron

Fertilising the Oceans with Iron

A correspondent has brought THIS ARTICLE to my attention. He did it for two reasons: 

  1. It is a very interesting article and 
  2. My photograph of Banded Iron Formation which I wrote about some time ago, is used to illustrate it. See HERE.
The first reason is the more important one - of course. 

I didn't realise how complicated the chemistry of iron in the oceans and atmosphere was. Iron is the fourth most abundant element in the Earth's crust but is almost absent in the oceans. Its absence can hinder the growth of diatoms and other beasties. If there was more iron available, more diatoms could form, removing carbon dioxide from the atmosphere. Sounds simple, but it is not. Read the article to understand some of the complications!

Iron-rich dust launched into the air by winds swirls around the Southern Ocean. Understanding how iron’s chemistry shifts during its journey from earth to air to sea will be important for developing better climate models. (William Putnam and Arlindo da Silva, NASA / Goddard Space Flight Center)

Monday, 30 December 2019

DOWN TO EARTH EXTRA - JANUARY 2020


DOWN TO EARTH EXTRA - January 2020


You can get the latest edition HERE.



PROPOSED TWO INDOOR COURSES IN MARCH 2020

Proposed Two Indoor Courses in March 2020

Nick Chidlaw has contacted me about two courses he would like to run in Thornbury in early March.

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Information on courses
I am currently offering two 1-day courses for next March; these are indoor-based, and describe field areas where I have organised events in the past. These courses may be attractive to people who are not in a position to visit these areas e.g. insufficient time available because of family / work commitments, or health problems.
Details of each course is provided at the bottom of this message.
Each course would comprise powerpoint-based lectures, together with examination of hand specimens of relevant mineral and rock types, and published geological maps of the field areas. The hand specimens have been collected by the tutor in the field areas described.
A handout outlining the day’s programme containing sketch maps and other relevant drawings, stratigraphic tables and a list of optional reading,  would be provided on each course. No prior knowledge of geology or the study areas would be assumed.  
Please note that these courses are run on the same weekend and in the same venue, but are independent of one another – you can enrol on both if you wish to, or one of them, according to your interests / availability.
Venue for both courses
The Buckingham Room (single storey building by the car park) at The Chantry, 52 Castle Street, Thornbury, South Gloucestershire. BS35 1HB. See website for further details www.thechantry.org.uk

I will provide Information on accommodation options to those who live beyond reasonable commuting distance. 
On each course, attendees would bring their own packed lunch and other refreshments, or go into the town for lunch.  
Tuition Fee 
£27.00 per person for each course.
Payment of Tuition Fee
Cheque payable to me sent to 8, Silver Street, Dursley, Glos. GL11 4ND. Bank Trans can be arranged if required (let me know).
Deadline for viability of both courses 
Saturday 1st February (5 weeks before the courses are due to run).
Both courses to have a minimum of 10 attendees / fee equivalent. Maximum of 30 attendees on each course. If viability for either or both courses is reached, those enrolled will be informed on the deadline date and arrangements will be able to continue. Further enrolments can be made up to 1 week before the courses are due to run. If the minimum number of attendees / fee equivalent is not reached for either course by the deadline, that course will be cancelled and fees received will be returned to those who have sent them in.
Any queries, do get in touch with the tutor nickchidlaw@gmail.com

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PERMIAN STRATA IN NORTH EAST ENGLAND: continental dune fields, marine reefs and karstic collapse


Permian Slump Olistolith, Trowe Point

Saturday 7th March 10.00 am – 5.00 pm
During the Permian period (299 – 252 million years ago), the crust that became the British Isles was located just north of the equator, under a hot, dry climate. Here, continental environments characterised the period, except in parts of north, where in Mid and Late Permian times episodic marine incursions laid down mostly carbonate sediments with interbedded evaporites. In the north east of England, Permian strata of both continental and marine origin are well represented and exposed, particularly along the attractive coastline. They are impressive, reflecting a variety of environments: continental dune fields, succeeded by both deep and shallow water shelf deposits, including an extensive bryozoan reef belt 20 miles long and up to 100m high. In some of the marine strata, fish, land plants and land reptile remains are preserved. Localised as well as extensive wholesale landsliding of the marine shelf  is evident. In what are now the onshore areas, the evaporites (chiefly halite and anhydrite) were subsequently mostly dissolved, forming impressive collapse features. Bizarre concretionary structures, which may have developed in much more recent geological times, characterize some of the carbonates.      

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METAMORPHISM AND MINERALIZATION IN THE BRISTOL – MENDIP AREA

Pb & Zn Ores with Calcite, Radstock Museum

Sunday 8th March 10.00 am – 5.00 pm
Following the end of the Carboniferous period around 300 million years ago, the area of the earth’s crust that became the British Isles began to stretch and heat as the North Atlantic Rift basin began to form. In the west of England, subsiding rift basins developed where the Cotswolds and Somerset Levels now lie. Between these places, in the Bristol – Mendip area, the crust was under tension at times, causing opening of lines of weakness including faults, joints and fissures. Into these created spaces, and cave systems, descending and ascending chemical –rich fluids accumulated, cooling and crystalizing to form mineral deposits. They include deposits of iron and manganese in Triassic times, and chiefly lead and zinc sulphides in Middle Jurassic times. Associated with the latter, other fluids spread extensively through porous strata in some areas, metamorphosing them to a silica-rich rock. Subsequently, many of these mineral deposits became of significant economic importance to man. This course will familiarise attendees with the history and character of this mineralization, and the impressive variety of mineral types that have been collected in the area in the past.