Skip to content

Pyroclastics 101 - DP/EC one-o-one EarthCache

Hidden : 10/23/2017
3 out of 5
3.5 out of 5

Size: Size:   other (other)

Join now to view geocache location details. It's free!


How Geocaching Works

Please note Use of services is subject to the terms and conditions in our disclaimer.

Geocache Description:

Flag Counter


Pyroclastic rocks or pyroclastics 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. Pyroclastic rocks may be a 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 (Source: Blatt, Harvey and Robert J. Tracy (1996) Petrology: Igneous, Sedimentary, and Metamorphic, W.H.W. Freeman & Company; 2nd ed., pp. 26–29; ISBN 0-7167-2438-3)

Source: Heiken, G. and Wohletz, K., 1985 Volcanic Ash, University of California Press, pp. 246

To claim your find:

  1. At the GZ coordinates you are in front of:
    1. Fine tuff
    2. Coarse tuff
    3. Lapilli tuff
    4. Agglomerate
  2. What is the max size of clast you can see?
    1. > 100cm
    2. > 50cm < 100 cm
    3. >10 cm < 50 cm
    4. > 1 cm < 10 cm
    5. A mixture of all sizes
  3. What is the predominant colour of the matrix of this rock? (the thing that holds the clasts together)
    1. Green
    2. Yellow
    3. Grey
    4. Red
    5. Purple
    6. Brown
  4. What colour predominates amongst the clasts?
    1. Blue
    2. Red
    3. Brown
    4. Yellow

If you think you know all the answers, please log your found but send me, through my profile, the answers (*). If they are correct, you will not hear from me again but know that I truly appreciate you taking the time to visit this corner of the world and I hope that you have learnt a little bit more about the geological processes that take place on the surface of the earth. If they’re wrong I will send you an explanatory note showing you where you went wrong. If you don’t send the answers, your log will be deleted without any explanation.

(*) Please note that when you e-mail me, please supply the reference (GC7DZB7) and name (Pyroclastics - DP/EC one-o-one) of the cache and please click on the “I want to send my e-mail address along with this message” so that when I reply to you the messages don’t go into e-mail heaven (or hell).

Rochas piroclásticas ou piroclástos são rochas clásticas compostas unicamente ou principalmente de materiais vulcânicos. Onde o material vulcânico foi transportado e retrabalhado através de acção mecânica, como por vento ou água, essas rochas são denominadas vulcaniclasticas. As rochas piroclásticas podem ser uma variedade de granulometrias, desde os maiores aglomerados até cinzas e tufos muito finos. Piroclastos de diferentes tamanhos são classificados como bombas vulcânicas, lapilli e cinzas vulcânicas. Cinza é considerado piroclástico porque é um pó fino feito de rocha vulcânica (Adaptado de: Blatt, Harvey and Robert J. Tracy (1996) Petrology: Igneous, Sedimentary, and Metamorphic, W.H.W. Freeman & Company; 2nd ed., pp. 26–29; ISBN 0-7167-2438-3)


Adaptado de: Heiken, G. and Wohletz, K., 1985 Volcanic Ash, University of California Press, pp. 246

Para validar o teu registo, responde às seguintes perguntas:

  1. Nas coordenadas do GZ estás na frente de:
    1. Tufo fino
    2. Tufo grosseiro
    3. Tufo lapilli
    4. Aglomerado
  2. Qual é o tamanho máximo de clasto que podes observar?
    1. > 100cm
    2. > 50cm <100 cm
    3. > 10 cm <50 cm
    4. > 1 cm <10 cm
    5. Uma mistura de todos os tamanhos
  3. Qual é a cor predominante da matriz desta rocha? (o que mantém os clastos juntos)
    1. Verde
    2. Amarelo
    3. Cinzento
    4. Vermelho
    5. Roxa
    6. Castanho
  4. Qual a cor predominante entre os clastos?
    1. Azul
    2. Vermelho
    3. Castanho
    4. Amarelo

Se achas que sabes todas as respostas, por favor faz o teu log de “found”, mas ao mesmo tempo envia-me as respostas a estas perguntas (* - ver em cima).
Se estiverem correctas, não respondo mas fica sabendo que eu estimo a tua visita a este cantinho da terra e espero que esta cache sirva para desvendar mais um mistério dos processos geológicos da nossa bola azul. Se estiveram erradas, vais a exame novamente e levas com TPC’s extras. Porém se não enviares as respostas, simplesmente apago o log.


aThe most exciting way to learn about the Earth and its processes is to get into the outdoors and experience it first-hand. Visiting an Earthcache is a great outdoor activity the whole family can enjoy. An Earthcache is a special place that people can visit to learn about a unique geoscience feature or aspect of our Earth. Earthcaches include a set of educational notes and the details about where to find the location (latitude and longitude). Visitors to Earthcaches can see how our planet has been shaped by geological processes, how we manage the resources and how scientists gather evidence to learn about the Earth. To find out more click HERE.

Additional Hints (No hints available.)