Rocks from the Bishop Tuff, uncompressed with pumice on left; compressed with fiamme on right.

Flight through a µCT-image stack of a Lapilli of the volcano Katla in Iceland. Find spot: Beach near Vik at the end of road 215. Acquisition done using "CT Alpha" by "Procon X-Ray GmbH", Garbsen, Germany. Resolution 11,2µm/Voxel, width circa 24 mm.

3D-Rendering of the above image stack, in parts transparent. Heavy particles in red.

Pyroclastic rocks or pyroclastics (derived from the Greek: πῦρ, meaning fire; and κλαστός, meaning broken) are clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic. Commonly associated with unsieved volcanic activity–such as Plinian or krakatoan eruption styles, or phreatomagmatic eruptions–pyroclastic deposits are commonly formed from airborne ash, lapilli and bombs or blocks ejected from the volcano itself, mixed in with shattered country rock.

Pyroclastic rocks may be composed of a large range of clast sizes; from the largest agglomerates, to very fine ashes and tuffs. Pyroclasts of different sizes are classified as volcanic bombs, lapilli and volcanic ash. Ash is considered to be pyroclastic because it is a fine dust made up of volcanic rock. One of the most spectacular forms of pyroclastic deposit are the ignimbrites, deposits formed by the high-temperature gas and ash mix of a pyroclastic flow event.

Classification of Pyroclasts^[1]

Three modes of transport can be distinguished: pyroclastic flow, pyroclastic surge, and pyroclastic fall. During Plinian eruptions, pumice and ash are formed when silicic magma is fragmented in the volcanic conduit, because of decompression and the growth of bubbles. Pyroclasts are then entrained in a buoyant eruption plume which can rise several kilometers into the air and cause aviation hazards. Particles falling from the eruption clouds form layers on the ground (this is pyroclastic fall or tephra). Pyroclastic density currents, which are referred to as 'flows' or 'surges' depending on particle concentration and the level turbulence, are sometimes called glowing avalanches. The deposits of pumice-rich pyroclastic flows can be called ignimbrites.

A pyroclastic eruption entails spitting or "fountaining" lava, where the lava will be thrown into the air along with ash, pyroclastic materials, and other volcanic byproducts. Hawaiian eruptions such as those at Kīlauea can eject clots of magma suspended into gas; this is called a 'fire fountain'. The magma clots, if hot enough may coalesce upon landing to form a lava flow.

Pyroclastic deposits consist of pyroclasts which are not cemented together. Pyroclastic rocks (tuff) are pyroclastic deposits which have been lithified.

References[link]

This biographical article needs additional citations for verification. Please help by adding reliable sources. Contentious material about living persons that is unsourced or poorly sourced must be removed immediately, especially if potentially libelous or harmful. (November 2010)

GP (Graham Peter) Hall (born 15 July 1943, Hampton Hill, London, UK)^[1] is an English guitarist, composer and improviser fusing and mixing both traditional and avant-garde styles. He is also known for having invented the musical genre known as 'Industrial Sound Sculptures'.^[2]

Musical style and techniques[link]

Hall's music draws on classical, rock, jazz, flamenco, folk and blues styles as well as free music, electronic noise and "found" instrumentation.^[3] He uses slide and fingerpicking techniques but also plays (or prepares) his guitars with various found implements such as crocodile clips, palette knives, velcro strips, an antique psaltery bow, wind-up toy cars and others in order to create a variety of different sounds and attacks.^[3][4][5] Hall uses a variety of treatments and electronic effects pedals to further process his guitar output, and sometimes incorporates radio broadcasts into his ensemble sound.

Some of Hall's techniques resemble those of avant-garde guitarist Keith Rowe (who also plays guitar with found implements and incorporates radio broadcasts into his work). However, Hall's approach is less orientated towards free jazz and tends to be more melodic, serving a tune or the background setting of a melody. Unlike Rowe (who generally plays - or manipulates - his guitar with the instrument lying flat on a table) Hall performs using the standard playing position, although he has been known to lay his guitar down flat when using the wind-up toy cars.^[3]

Hall refers to one of his main playing approaches as "Industrial Sound-Sculpture". This involves creating a highly detailed and layered impressionistic sound piece by layering and/or looping guitar sounds and signals created by a variety of standard and non-standard methods. The sound-sculptures can be melodic, amelodic or both.^[4]

Although his electric and electronic playing gains the most attention at concerts, Hall is also known for his particular virtuosity as an acoustic guitarist (on both steel-strung and gut/nylon strung instruments). He is an expert flamenco guitarist, and an accomplished classical-style player. He also plays a customised Shergold six-string bass guitar featuring a half-fretted, half-fretless fretboard (and has been known to play it using flamenco techniques). Hall has been known to dabble in playing other instruments such as double bass, piano, soprano saxophone and varied percussion, mostly for the sake of their timbral qualities. More recently, he has taken up singing (in order to perform his own original folk songs).

History[link]

1960s and early 1970s - blues etc.[link]

Raised in the East End of London, Hall was schooled in classical, flamenco and jazz playing and went on to develop his skills as a guitarist in the British blues boom of the late 1960s (he would also be inspired by the developing hard rock scene). As a teenager, he played in the Odd Lot Band and set up the Odd Lot Club as a venue for their music, which in turn attracted more established bands and players for concerts.^[5]

As he became better known, Hall went on to play at more celebrated London venues including The Roundhouse, the Middle Earth club and the 100 Club (where he was a resident player). He supported the likes of Deep Purple, The Hollies, and Chris Farlowe and played on stage with original American blues heroes John Lee Hooker and Sonny Boy Williamson.^[6] In the early 1970s Hall toured Europe as guitarist for Casey Jones & The Governors (a blues-pop band previously known as Casey Jones & The Engineers, in which both Tom McGuiness and Eric Clapton had played briefly before moving onto Manfred Mann and The Yardbirds respectively).

1970s - into the avant-garde[link]

Hall's musical approaches began to broaden in the early 1970s. He spent some time living with Romani musicians (studying with renowned flamenco guitarist Manitas de Plata)^[5][6] and subsequently became involved in more avant-garde work, writing, producing and performing regularly at the British East/West Centre in London.^[5] He also became the musical director for the multi-media performance art group Welfare State International.

In 1972, Hall was commissioned by the South Hill Park Arts Centre in Bracknell to write The Estates - a "large and complex" musical piece intended to depict the breakdown of established communities to make way for the New Town of Bracknell. The piece was scored for a large ensemble centred around guitar, bass, clarinet, glockenspiel, hammer dulcimer, assorted percussions and two specially prepared piano frames. The Estates was recorded and released on album by Prototype Records in 1972. Originally an hour long, the recording was subsequently edited down to twenty-five minutes, and a version was released twenty-five years later on the Mar Del Plata album in 1997. Video footage also exists but has not been commercially released.^[1][6]

In 1975, Prototype Records released Manifestations, another album of Hall's work.

Mid-1970s to mid-1980s - wilderness years[link]

At around this time, Hall's promising career was cut short by personal trauma. He describes it as having been "traumatised by a situation of events beyond my control... I was in the wrong place at the wrong time and the experience left me mentally, physically and spiritually bankrupt. As the trauma took hold, it took my confidence and self worth." He was driven to alcohol and to what he describes as "other escape mechanisms that took me to places I didn't want to go."^[6] Hall spent a fifteen-year period in personal and material decline. He suffered from depression and became homeless and destitute on several occasions until joining a recovery programme. During the 1980s he began to "communicate back into the real world via my music... at first it was a real hard slog. But as if to compensate, I had extraordinary insights. I am sober today and lead a relatively ordinary life and I really value that. I could not perform my music in any other way other than with a clear head, because it requires so much concentration. It was an isolated and lonely road, but I do appreciate the people who helped me in financial and supportive ways and gave me encouragement when I had many setbacks."^[6]

In 1986, Hall released a new album - the twenty-nine track Colors (Movements) - as part of the Colors series of instrumental albums on the Kenwest label (some of his pieces were also included on the compilation album for the range, Colors: The Collection). During this period he also composed library music (which suited his individual and colouristic style with its multi-instrumental and gadgetry-filled approach).

1990s - renaissance[link]

Hall's next solo album, Imaginary Seasons, arrived on his own Imaginary Music label in 1995^[1] and was a surprise nominee for the Mercury Music Prize. Having signed to the Future Music Recordings label, Hall delivered a further follow-up in 1996 - Figments Of Imagination,^[1] which compiled both new pieces and old 1970s and 1980s recordings with various avant-garde musicians. In the same year, Hall appeared on the Unknown Public compilation CD Eclectic Guitars (alongside Frank Zappa, Bill Frisell, John Zorn and Robert Fripp) and performed a well-received live solo set at the Unknown Public Holiday event at the Queen Elizabeth Hall, London (26 September 1996).

1997 saw the release of two GP Hall albums - Mar Del Plata^[1] (a similar album to Figments Of Imagination, compiling both old and new tracks) and the live recording Marks On The Air^[1] taken from the accompanying small tour. (The second of these was released on the tiny Esoteric Binaural Label, and featured label owner and sound engineer Mike Skeet's individual take on binaural recording techniques). Hall also played concerts in the Scottish isles of Lewis and Harris, having been commissioned to write the commemorative piece Sea Sorrow. The latter appeared on the 1998 double album Steel Storms And Tender Spirits, which featured one disc of hard-textured, mainly electric material and one disc of softer, more acoustic-orientated pieces.

Having parted company with Future Music Recordings, Hall released the Each A Glimpse And Gone Forever album in 1999 on Esoteric Binaural Label. This was a part-live, part studio recording documenting activities and ideas generated by the 1998/1999 tours and featured collaborations with Justin Ash (ethnic instruments and percussion).

2000s - the maverick[link]

Without a steady recording contract, Hall's work in the subsequent decade became more sporadic. During 2000, he performed at Reading Jazz Club and at The Outsiders Festival in Oxford with John Ellis). He returned to Oxford in 2001 for a solo concert at The Jacqueline du Pré Music Building. In 2002, Hall performed a solo tour called “Moving The Mountain” which took in Didcot, London, Southend, Bristol, Reading, Oxford, Liverpool and a return to the Isle Of Lewis. He also performed at the Burning Shed Event in Norwich (in support of Industrial Blue, a compilation of his more industrially-inclined work released on the Burning Shed record label).

During 2003 and 2004 Hall recorded two as-yet-unreleased song albums - Songs from the House Within and Precious Love. His next actual release, however, was Gothic Flamenco which was released on the Bronze Records label in 2005 and continued his eclectic instrumental approach. Hall performed live at the 2005 London Guitar Festival. In 2006, he produced a couple of self-released DVD recordings - the acoustic-based Guitarist and the more avant-garde Electric, both filmed by Peter Remke at the Hope & Anchor venue in North London.^[7]

Since then, Hall has toured and played intermittently, now interspersing his instrumental pieces with original self-written folk songs. His latest release is the 2010 album Pyroclastic Flow, a fifteen-track guitar-only CD which explores most styles of guitar work. Five years in the making, the album was a collaboration with Hall's close friend Alistair Michie, the Scottish abstract painter. Hall commissioned Michie to paint the covers of the CD - although Michie died just before he could finish the paintings, they are still being used as album artwork as a posthumous tribute. Various other future GP Hall albums have been promised but not yet released - these include the all-acoustic Pure and a Delta blues record. Recently, he has been gaining attention from a new audience by showcasing video clips of his playing on YouTube.

Collaborations[link]

Hall has worked with (among others) Lol Coxhill, Paul Rutherford, Jeff Clyne, John Ellis and Lyn Dobson.^[2]

Discography (selected)[link]

Albums[link]

• The Estates (1972 Prototype Records)
• Manifestations (1975 Prototype Records)
• Colors (Movements) (1986, Kenwest)
• Imaginary Seasons (1995, River Flow Productions)
• Figments Of Imagination (1996, Future Music Records)
• Mar Del Plata (1997, Future Music Records)
• Marks On The Air(1997, Esoteric Binaural Label) - live album
• Steel Storms (And Tender Spirits) (1998, Future Music Records)double CD
• Each A Glimpse (And Gone Forever (1999, Esoteric Binaural Label) - mixture of studio and live tracks
• Industrial Blue (2002, Burning Shed)
• Gothic Flamenco (2005, Bronze Records)
• Pyroclastic Flow (2010 Imaginary Music)

(Note that the majority of GP Hall's catalogue has consisted of short-run release albums which have been deleted fairly quickly, meaning that many recordings of individual pieces have been re-released on subsequent recordings.)

appearance on various artist compilations[link]

• Colors (The Collection) (1986, Kenwest)
• Eclectic Guitars UP6 (Unknown Public)

DVDs[link]

• Electric (2006, self-released)
• Guitarist (2006, self-released)

References[link]

External links[link]

• GP Hall homepage
• GP Hall @ MySpace
• GP Hall blog
• GP Hall YouTube channel
• Review of GP Hall showcases on Vortex jazz venue homepage