The

HAMMEHAMMERR

Eruption in the Land of Fire and Ice

Antarctica—The Final Frontier???

A visit to the Todd’s Road area to investigate reports of a Sink Hole

GSTT Career Day

GSTT members at the 2010 AAPG Conference

July 2010

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Editor’sEditor’s NoteNote Welcome t o the July Issue of the Hammer! Welcome t o the July Issue of the Hammer! Welcome t o the July Issue of the Hammer! In th is issue, we t r avel f r om the volcanoes of Ice land to the iceber gs of Ant ar ct ica with a few s t ops in be tween. On our journey, we f ind t ime to s t op of f at Todd’s r oad in centr a l Tr in idad to inves t igat e some s tr ange geologic happenings and we even c hec k out the AAPG conference in New Or leans. R ipe wi th geologic act iv i ty, the pas t months have seen intense ear thquakes in Chi le and Hait i and magnif icent volcanic erupt ions in I ce land, br inging geology, in a l l i ts forms, int o the l imel ight . These e vents cer t a in ly remind us of the sheer s t rength and pow er of the Ear th w e al l love to s tudy and explore. With th is in mind, I ur ge you al l to go out and do geology pr oud, whe ther i ts your hobby, pr ofession or both! Many thanks to a l l who contr ibuted and inspi red the ar t ic les in th is issue and I look for war d to a l l new and cont inued suppor t .

AnnaAnnaAnna---Lisa ThomasLisa ThomasLisa Thomas

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Table of contentsTable of contentsTable of contents

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Eruption in the Land of Fire and IceEruption in the Land of Fire and IceEruption in the Land of Fire and Ice

A Visit to the Todd’s Road Area to Investigate A Visit to the Todd’s Road Area to Investigate A Visit to the Todd’s Road Area to Investigate report of a Sink Holereport of a Sink Holereport of a Sink Hole

AntarcticaAntarcticaAntarctica———The Final Frontier??The Final Frontier??The Final Frontier??

GSTT Members at the 2010 AAPG ConferenceGSTT Members at the 2010 AAPG ConferenceGSTT Members at the 2010 AAPG Conference

GSTT’s Career Day SeriesGSTT’s Career Day SeriesGSTT’s Career Day Series

Past Event HighlightsPast Event HighlightsPast Event Highlights

GSTT StoreGSTT StoreGSTT Store

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Eruption in the Land of Eruption in the Land of Fireireire andand

EYJAFJALLAJÖKUL!EYJAFJALLAJÖKUL!EYJAFJALLAJÖKUL!

This may sound like a profanity and it was indeed treated like one by most people travelling to and from Europe throughout the month of April. Many can’t even call it by its name but the recent eruption of this South Iceland volcano was enough to bring activity in European airspace to a halt for several days. Belting out an ash cloud that

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travelled over 30,000 ft, Eyjafjallajökul stands at an impressive 5,465ft high. It is a typical stratovolcano displaying effusive type eruptions, characteristic of volcanoes found on d i v e r g e n t p l a t e boundaries such as that found on Iceland. Iceland straddles a text book example of a divergent plate boundary – the boundary between the American and Eurasian Plate, also known as the Mid-Atlantic Ridge. Simple put, Eyjafjallajökul’s eruptions are relatively quiet and slow moving.

Meaning “island mountain under glacier” in English, the volcano is

located as it says…under a glacier. This makes for an interesting combination of fire and ice. Magma erupting under the ice sheet is hot enough to melt the overlying ice, forming steam. It was this steam that caused Eyjafjallajökul’s explosive eruption, propelling ash and volcanic gases over several thousand feet into the air.

SO WHAT MADE EYJAFJALLAJÖKUL’S ERUPTION SO EXPLOSIVE THIS TIME?

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What’s also interesting about Eyjafjallajökul is that its actual eruptive phase began almost one month prior to the closure of Euro-airspace. Increased seismicity began during the month of March with the first visual report being recorded on March 20th. During this time most of the eruption came from the flanks of the volcano. The explosive eruption began on April 14th with the eruption coming from the central caldera. This central caldera boasts the thickest section of glacial ice, hence the devastating results.

During April, b r e a t h t a k i n g i m a g e s o f Eyjafjallajökul’s s p e c t a c u l a r l i g h t n i n g storms were amongst the most circulated images around t h e g l o b e . Created due to e l e c t r i c i n t e r a c t i o n s between the

One can compare Eyjafjallajökul’s recent One can compare Eyjafjallajökul’s recent eruption to a tiger stalking its prey in the wild…eruption to a tiger stalking its prey in the wild… ......extremely dangerous yet strangely beautifulextremely dangerous yet strangely beautiful

Eyjafjallajokul’s lightning storms

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volcano’s hot ash clouds and the cold surrounding atmosphere, these lightning storms were in no short supply. With such devastating beauty captured on film, Eyjafjallajökul, a common tourist destination in its dormant phase, will definitely see a rise in popularity in coming years. Yet, ironically enough, Eyjafjallajökul is actually considered one of Iceland’s most minor volcanoes, boasting only three previous major eruptions, one of which went on intermittently for a whopping 14 months! From December 1821 to January 1823, the volcano’s series of explosive eruptions expelled ash that can still be found in the rock record through South Iceland. Being the volcanic hotspot that it is, Iceland boasts o v e r 2 0 0 volcanoes. With so many volcanoes, it’s no wonder that Eyjafjallajökul is considered minor! The major stars amongst Icelandic volcanoes are the Hekla, Katla and Grimsvotn with Hekla and Katla being known as the Two Two Two Angry SistersAngry SistersAngry Sisters. Eruptions from these volcanoes have each produced their own catastrophic results, with some eruptions killing over 9,000 people.

Mount Hekla in its dormant stage

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What’s particularly worrying about Eyjafjallajökul is that it’s considered to be an opening act for neighbouring Katla. Every Eyjafjallajökul eruption or simple disturbance has been followed by a Katla eruption. Katla holds a terrifying history, with over twenty documented eruptions. Located under 1600ft of ice known as the Myrdalsjoekull glacier, Katla stands at 4,961ft high and has a crater over 10km in diameter! From sheer volume alone, it’s clear to see how devastating an explosive eruption from Katla

would be. Mass flooding from glacial melt alone would create massively disastrous effects.

F o r t u n a t e l y n o disturbances on Katla have been recorded, yet all eyes remain on Katla as Eyjafjallajökul continues on its terrible tantrum.

Anna-Lisa Thomas

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As a result of recent heavy rains, extensive

flooding took place along the Caparo River in the

Todd’s Road and Palmiste area. When the water

receded it was discovered that an old railway

right of way used as a roadway had disappeared

in one place. The media and residents started

using a number of terms to describe what they

believed had happened, however their usage of

those words was incorrect. According to the

Glossary of Geology by the American Geological

Institute (1987) a Sinkhole is a circular

depression in a karst area. Its drainage is subterranean and is commonly funnel

shaped. While a Canyon is a long deep, relatively narrow steep sided valley

confined between lofty and precipitous walls in a plateau or mountainous area.

Map showing the location of the collapsed road (red dot) at Todd’s Road.

A Visit To The Todd’s Road Area

To Investigate Reports Of A Sinkhole

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A visit to the site (no Police as the media reported) revealed an amazing landscape. As

one walked along the road, the vegetation suddenly open up and an extensively

worked quarry was seen. Drains ran parallel to either side of the road, suddenly the

road ended in what appeared to be space. Large tension cracks were noticed parallel

to the edges and extending towards the center of the road. Water from the drains was

seen to be falling over the edge like a waterfall into a deep pit, at the same time loud

noises were occurring regularly. This turned out to be large blocks of sand and clay

falling off the edge of the road into the pit, of course we immediately stepped back to

fracture free road. The low point of the quarry was flooded, reportedly to a depth of 80’

in places.

The features seen led to some idea how it all occurred. Excessive and uncontrolled

quarrying of sand took place up to the edges of the road ( out of sight out of mind! ),

flooding of the Caparo river allowed significant amounts of water to flow down the

drains, the eastern one flowed over into the pit eroding and undermining the

unconsolidated sand beds, water from the western drain flowing through a

underground drain did the same thing. Ultimately the road started collapsing,

accelerating the erosion on either side. All the water flowing into the pit filled up the

low point. It is anticipated that with further rainfall and flooding expected this year,

this erosion will continue with the size of the collapse expanding.

A panoramic view of the collapsed road and flooded quarry.

In the Todd’s Road area the rocks belong to the Talparo Formation, the sand belongs to

the SumSum Member. The Talparo may be as much as 4000’ in thickness with a number

of thick and laterally continuous sand bodies. It has been encountered from the

Venezuelan side of the Gulf of Paria to the east coast of Trinidad. An almost continuous

(44 km.)

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Surface geological map (Kugler 1959)

outcrop (surface exposure) stretches from Claxton Bay in the west to Cumoto in the

east. The SumSum sand averages 100 – 150’ thick with a maximum of 200’, in parts of

the Gulf of Paria two sands are encountered.

This sand is of great economic importance to Trinidad, firstly it has served as a source

of building material and secondly as a source of potable water. The recent house

building boom of the last 9 years has had a number of unintended and unplanned

consequences. Significant areas through central Trinidad have been affected by

quarrying. In places like Claxton Bay- Soledad Road, almost all of the sand has been

removed right down to the basal clay. Old Caroni quarries at Diamond Road were

reopened, significantly expanded and once again in places quarried down to the basal

clay. Using Google Earth one can also see the scale of the quarrying in the Ravine

Sable / Caparo area. In this area the sand has also been removed to the basal clay in

places, which would allow water to collect above it.

The most immediate impact of the quarrying is on the availability of water. The

exposed sand served as the area (catchment area) where rain was able to soak into

the ground, percolate downwards and be stored. A number of water wells exploit this

aquifer in Claxton Bay (SumSum Hill), the water is used by both for residential

purposes and by Petrotrin. Where the sand has been completely removed very limited

recharge of the aquifer is possible in that area, leading to the water wells being

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What can be done with this area if quarrying is not restarted? The area is a

topographic low surrounded by hills that originally was swampy. Quarrying

emphasized and expanded this low area. This incident has provided an opportunity to

mitigate a number of problems.

The perennial problem of flooding can be reduced if the quarry is converted to a

reservoir where flood waters can be diverted and stored. This can be accomplished by

the construction of a dam across the mouth of the valley and an arbitrary fill line of

the 50m contour used. The outline of the proposed reservoir is dependent on the new

topography resulting from quarrying. The stored water can either be discharged when

the floods abate, used during the dry season for irrigation and recharge of fresh water

aquifers.

Some kind of geotechnical work needs to be done to estimate the volume of material

removed over time, the amount that remains and its location. If it is decided to restart

mining, a better exploitation and rehabilitation plan can be designed using this data.

In the short term the amount of water falling into the pit needs to be reduced.

Curtis Archie

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ANTARCTICAANTARCTICAANTARCTICA ——— The Final The Final The Final FrontierFrontierFrontier??????

ith Trinidad’s past drought and in-

tense heat, a visit to Antarctica may not

sound so crazy. Most of us would be glad

to take it in for a day. We would compare

it to standing in front of an open freezer

for a few minutes. Just enough to cool off,

we might think….it’s soooo hot……But

let’s turn that one day into almost two

weeks. How many of us would be on

board then? Indeed, just a select few of

us would ever make those steps to take

a full fledged expedition to Antarctic. One of these elite few include the

GSTT’s past president Dr. Krishna Persad whose February expedition to the

coldest driest continent on Earth forged the inspiration for a closer look into

Antarctica.

w

So why Antarctica?????

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Called the final frontier, Antarctica is

the coldest, driest continent on Earth.

Temperatures can reach lows of -80

degrees Celsius in the winter months

and high of a max of 15 degrees Cel-

sius in so-called “summer”. Total

rainfall for the year measures on av-

erage about 0.25cm. To put this into

perspective, Trinidad average annual

temperature is 30 degrees Celsius and

receives 25cm of rainfall for the year.

Such conditions, make Antarctica one seriously cold desert!

Climate varies across the continent with the coldest and driest being

within the interior. While the coast and Antarctica Peninsula where Dr.

Persad traveled have relatively warmer and wetter conditions, overall

conditions still lie well within desert category.

What’s also interesting about Antarctica is its landscape. Antarctica has

a landscape like no other, with more than 99% of the land being covered

by ice. Because of this thick ice cover, Antarctica is the highest of all

Earth’s continents with an average elevation of an amazing 7500ft! Gla-

ciers actually cover much of Antarctica and form the continents major

Brr..It’s cold here……Brr..It’s cold here……Brr..It’s cold here……

Dr. Persad and his wife, Jasserani deep in Antarctica. Zipped up tight from the cold!

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ice shelves around the coast, including the Larsen ice shelf close to Ant-

arctica Peninsula.

With so many ice shelves around, Antarctica has many icebergs. Even

though the one that sunk the RMS Titanic was in the Northern Atlantic,

icebergs anywhere are dangerous. The largest iceberg ever recorded actu-

ally came from the Antarctica’s Ross Ice Shelf and was 13,000 km2 in

area! Aside from ships hitting them, icebergs can also turn over without

any warning, causing large tidal waves.

As dangerous as they are, icebergs can be picturesque and beautiful. One

highlight of an expedition to Antarctica is witnessing these beauties in

their true form. Dr. Persad even had the opportunity to kayak amongst

them!

………...Iceberg, right ahead!!………...Iceberg, right ahead!!

Whale of a time!Whale of a time!

Antarctica has no indigenous people…….none! People do live there though for the

cause of science! Antarctica is the home to over 5000 scientists and researchers.

Antarctica has no trees, bushes or shrubs….none! The only form of vegetation on Ant-

arctica are mosses and algae. In some part of the continent, algae are even known to

grow within rock pore spaces due to the strong dry winds!

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Antarctica has no land based animals…none! Antarctica’s waters how-

ever, are rich in wildlife with numerous species of whales, seals and

penguins. Any visit to Antarctica (which included Dr. Persad’s) will prove

to be full of whale, seal and penguin sightings.

These animals thrive in Antarctica because of the rich marine life. Ant-

arctica’s most famous animal has to however, be the penguin. Some

penguin colonies can be over 100,000 strong!

No geologist’s visit to Antarctica would be complete without understand-

ing the rocks.

Two geologic areas make up Antarctica- West and East Antarctica. East

Antarctica is a large Precambrian shield similar to those found in Bra-

zil, Africa and India. The rocks here are high grade metamorphics over-

lain by younger oceanic deposits.

Geology, geology, geology…Geology, geology, geology…

Deep in the penguin colony aren’t we, Dr. Persad!

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West Antarctica is relatively younger in age and consists of volcanic

sediments. Highly more tectonically active than its Eastern counterpart,

several active volcanoes occur here and rocks are of upper Palaeozoic to

Mesozoic age. West Antarctica is also more mountainous than East Ant-

arctica, with the Antarctica Peninsula actually being formed as part of

the Andean orogeny! The steep cliffs of the Antarctica Peninsula pro-

vided many a spectacular view on Dr. Persad’s expedition, including the

famous Neptune’s Window which is a break in these cliffs caused by a

lava flow.

So many more interesting aspects lie beneath Antarctica’s thick white

blanket! Hopefully many more of us can give Antarctica an up close and

personal look!

Anna-Lisa Thomas inspired by Dr. Krishna Persad

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GSTT members were in no short supply at this year’s AAPG conference held in New Orleans. President Elect, Mr. Curtis Archie recaps parts of his trip and some of the familiar faces he saw there.

GSTT President Sushma Chatelal with Dr. Ryan Ramsook. Dr. Ramsook is the recipient of a GSTT bursary for post-Doctoral research and is due to present to the membership at a date to be announced.

GSTT Members at 2010 AAPG

Conference

Have you presented a poster/paper at this year’s AAPG conference?? If so, the GSTT invites you to present to its membership. Email gstt@tstt.net.tt for details

Curtis Archie

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GSTT member, Tricia Alvarez presented a poster “ Tectonic Habitat of Hydrocarbons in the Deep- and Ultra-deepwater Frontier Areas of Trinidad and Tobago”.

GSTT members, Sarika Ramnarine and Kadira Singh taking in the conference.

Stefan Punnette, with GSTT past president, Dr. Krishna Persad. Mr Punette presented a poster “ Tectonic and Eustatic Controls on the Origin of Shelf Sands and Associated Facies, Offshore NCMA Area of Trinidad and Tobago”

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AAPG Latin American Region Meeting, attending were Sushma Chatelal (arrow pointing to) and Curtis Archie. Current Region President Enrique Velasquez introduced the assembled group, AAPG President J. Lorenz addressed all asking everyone to continue giving of their time to the organization.

Highlights of the AAPG Latin American Region Meeting

♦ Topics discussed were Education - including Geoscience Technology Workshops in the

region; AAPG short courses and regional lecturers. No distinguished lecturer is assigned to the region for another year. AAPG suggested that the region put together a list of po-tential lecturers from the region and anyone else they think would be suitable. Can more be done via teleconferencing? Ideas for topics?

♦ Creation and reactivation of student chapters and outreach to Universities. It was men-tioned that most visiting lecturers visit the St. Augustine campus in Trinidad.

♦ Creation of a young professionals committee. ♦ Country liaisons for each country with activity was discussed and volunteers asked for.

GSTT President Sushma Chatelal volunteered to be Trinidad & Tobago’s liaison. ♦ C. Archie mentioned that for the AAPG to be more effective the executive must be more

visible in the region, i.e. must visit countries. ♦ A potential problem with the region is that currently the executive is all from Colombia,

A. Guzman invited volunteers from all countries to serve.

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GSTT’s Career Day Series

For most of us, school days are a happy yet dis-tant memory. Indeed, some may forget how ar-duous and confusing the journey towards a career can be. With this in mind, GSTT members Johan Lall, Simon Paul, Sushma Chatelal and Nancy Gallai-Ragoobar went in search to enlighten the younger

St. Francois Girls Career Day ( recounted by Johan Lall ) Aisha and I presented to students at St. Francois Girls early in March, and it really was a fun experience. The enthusiasm of the Form Three students was a pleasant surprise, and it was refreshing to spend part of my work day in an environment where I was not the “Junior” – where I was the authority on the subject at hand, in this case, Geology.

Naparima Girls High School (recounted by Nancy Gallai-Ragoobar) We were asked by Mrs. Joanne Deokie (Geography teacher at the school) to give a talk / presentation to Form Three students. We prepared slides /notes for the respective disciplines and made the session interesting by awarding prizes to students who answered questions correctly. At the start of the session, we passed around brochures to inform the students about GSTT. We did power point presentations on the various disciplines for a period of approximately 10 minutes each and questions were answered at the end of each presentation. The content of the slides informed the students of the core duties and responsibilities of each discipline the pre-requisites (subject areas and grades) for entry level into University to pursue careers in the Geosciences and Petroleum Engineering.

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Our presentation was short, but

gave a complete introduction to

the field of Geoscience. Most of the

students didn’t have any prior

ideas about geology, much less for

considering it as a career. To help

them out, we gave guidance on the

choices of career within geology,

and the educational path to

getting there. I’m not sure if it

was the pretty colours on the

slides that kept their attention (we used those on purpose), or because we gave out “free stuff”, but

the kids seemed genuinely interested in what we were saying. The girls asked lots of questions and,

at the end of the session, when we asked how many future geologists were in the room, most of the

girls had their hands up. I guess we must have done something right.

If you are interested in giving a talk to a school ( can be of your choice or not), please feel free to contact the GSTT at gstt@tstt.net.tt

Students from St. Francois Girls’ High School showing of their brochures

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he Geological Society of Trinidad and Tobago or GSTT is the

professional body representing the interests of geoscientists in the

Republic. It has long had an interest in fostering student development and to

that end it hosts numerous technical sessions and fieldtrips each year. On

February 4th the GSTT gave a generous donation of books, DVDs and other teaching materials to the University

of the West Indies St. Augustine Campus, for use especially by the university’s BSc Petroleum Geoscience

Programme in the Faculty of Engineering.

The Petroleum Geoscience Programme was

developed in 2002 at request of the local

oil and gas industry and attracts from of the

top students attending the UWI. Its intake is

specifically limited to fewer than 20

students each year. The materials were

presented at the Petroleum Studies Unit by

Mrs. Sushma Chatelal, president of the GSTT,

at an event jointly organised Javed Razack,

Krystal Ramdin, Jivanti Ramdular and

Khellon Hodge, who are all members of the university’s Petroleum Exploration Society, and Nazreen

PAST EVENT HIGHLIGHTS

UWI St. Augustine Book Handover

T

GSTT’s president, Ms Sushma Chatelal and treasurer, Ms. Samantha Singh with UWI lecturers and students.

Dr. Brent Wilson

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Mohammed of the GSTT Secretariat. They were received

by Mr. Wayne Bertrand, programme co-ordinator for the

Petroleum Geoscience programme, who handed them on

to Mrs. Linda Claudia De Four, Deputy Campus Librarian,

and Miss Allison Dolland, Librarian in Engineering and

Physical Sciences. Also in attendance were Miss

Samantha Singh, Treasurer of the GSTT, Dr. Angelus

Pilgrim, Head of the Department of Chemical

Engineering, Professor Richard Dawe, Head of the UWI’s

Petroleum Engineering Programme, and Dr. Brent

Wilson, Senior Lecturer in Petroleum Geoscience. The materials are already being requested by the eager students.

GSTT president, Ms. Sushma Chatelal, presents one of several books to programme coordinator, Mr. Wayne Betrand

Fully engrossed attendees at Mr. Brendan Figueira’s presentation “Gas Hydrates Indicators—Offshore Trinidad”. This talk was given at Kampo’s Chinese Restaurant on June 1st, 2010.

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GSTT’s president Ms Sushma Chatelal presents a token of appreciation to Dr. Roger Clarke, senior lecturer from Leeds University. This highly anticipated talk, titled “Seismic Attenuation in Hydrocarbon Exploration: Old Pitfalls and New Possibilities” had to be postponed due to flight restrictions in the UK from the Icelandic volcanic ash cloud. We’re glad to see that Dr. Clarke finally made it to our shores to give such a great talk!

GSTT’s first field trip for the year took its many attendees throughout the Northern Range to examine the existing metasediments. Guided by Mr. Curtis Archie and Mr. Sisnarine Seegobin, the stops included National Quarry’s Limestone Quarry, Blanchisseuse and Maracas Bay. A long but informative and fun day!!

Mr. Curtis Archie’s interpretation of What Were They Really

Thinking??!!

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The GSTT held the first in a series of short courses on June 21st-23rd. “Structural Styles in Petroleum Exploration” was facilitated by Dr. James D. Lowell, an expert in the field. Attendees came out from different sections of the G&G community and were treated to a full overview of structural geology as its applies to petroleum exploration. Reports on the course were very positive with Dr. Lowell’s course instruction being well received!

Attendees at GSTT’s recent short course, facilitated by Dr. James Lowell (pictured centre), are all smiles!

Look out for GSTT Upcoming Short Courses! The topic areas, dates and instructors are: ♦ Rock Physics for Seismic Reservoir Characterization, August 3rd-5th, Dr. T. Mukerji

♦ Geochemistry, August 23rd-25th, Dr. S. Talukdar

♦ Sequence Stratigraphy, September 23rd-25th, Dr. R. Sams

Also look out for GSTT’s Upcoming Family Day!!!!!

Upcoming Events

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GSTT STORE There are lots of new items at the GSTT Store!!

Geological Bound Book Fab Cover 4 3/4" x 7 1/2" This all-weather bound book comes equipped with 20 helpful reference pages. It has standard and metric rulers, along with numbered pages to keep you organized. The Geological Book has 160 pages (80 sheets). A photo scale and ruler are included. TT$ 146

16 oz. Chisel Point Rock Hammer by Estwing E3-16BLC • Shock-Reduction Grip • Forged handle and head • Cushion grip for extra comfort • Sharp cutting bit TT$ 269

Estwing leather hammer sheath for Chisel Point Hammers This leather hammer sheath is designed to fit on belts up to 2" wide. The button snap closure holds the hammer firmly in place. The leather construction prevents any rattling that is common with metal hammer holders. TT$ 46

Pyramex Ztek Safety Glasses & Mini Ztek Safety Glasses Recommended for use with all hand tools. These cost effec-tive safety glasses meet all safety requirements for hand tool use and also protect you from harmful UV rays. • Clear Lenses. • Soft non-slip rubber temple tips. • Integrated nose piece. • Lenses are coated for superior scratch resistance. • Lenses provide 99% protection against harmful UV rays. • Compliance: ANSI Z87.1-2003, CSA Z94.3 TT$ 32

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BELOMO 10x Triplet, Loupe, Hand Lens & Lanyard The lens on this triplet is 21 mm diameter, 19 viewable TT$ 226

Suunto MC-2 Global • Global Balancing System • Clinometer • Large mirror • Jewel bearing • cm or inch scales • Adjustable declination correction scale • Additional sighting hole for superior accuracy • Baseplate with magnifying lens and anti-slip rubber pads • Luminous two-color bezel ring • Detachable snap-lock in lanyard. Easy to detach for working with the map • Wristlock in the lanyard TT$ 594

Sand Grain Sizing Folder Pocket-sized folder enables the field geologist to quickly and accurately iden-tify grain size and shape, grain sorting, roundness, and sphericity of a sample. Consists of sphericity/roundness measuring chart; printed examples of well-sorted and poorly-sorted grain samples in fine, medium, and coarse ranges; four actual grain samples illustrating angular, subangular, subrounded, and rounded shapes; six grain size samples: silt, very fine sand, fine sand, medium sand, coarse sand, and very coarse sand. Measurement limits for granules, peb-bles, cobbles, and boulders indicated. TT$ 73

Simon And Schusters Guide to Rocks and Minerals Practical, concise, and easy to use, Simon & Schuster's Guide to Rocks and Minerals contains everything that the rock and mineral enthusiast needs to know. This filed guide is divided into two large sections--one devoted to minerals and one to rocks, each prefaced by a comprehensive introduction that dis-cusses formation, chemistry, and more. All 377 entries, beautifully illustrated with color photographs and helpful visual symbols, provide descriptions and practical information about appearance, classifica-tion, rarity, crystal formation, mode of occurrence, gravity of mineral, rock chemistry, modal classifi-cation fields, formational environments, grain sizes of rocks and much more. Whether you are a seri-ous collector or an information-seeking amateur, this incomparably beautiful, authoritative guide will prove an invaluable reference. 600+ pages in full color More than 1000 illustrations 7.5" x 4.5" Perfect size for field use. TT$ 145

For more on the GSTT Store, visit http://www.gstt.org