Messages In This Digest (4 Messages)

1.: Fw: Catastrophic Coincidence: Second Ever Example Of Contemporaneous From: Ma'rufin Sudibyo

2a.: APA YANG TERJADI ketika hujan turun ? From: meta utami
2b.: APA YANG TERJADI ketika hujan turun ? From: er_erhanz
2c.: Re: APA YANG TERJADI ketika hujan turun ? From: erika nurhansyah

Messages

1.: Fw: Catastrophic Coincidence: Second Ever Example Of Contemporaneous

Posted by: "Ma'rufin Sudibyo" marufins@yahoo.com marufins

Sun Jan 11, 2009 6:34 pm (PST)

Satu lagi kejadian tumbukan benda langit dan vulkanisme basalt yang koinsidens waktunya. Dan baru berlangsung "kemarin sore' (30 juta tahun silam), bandingkan dengan kejadian tumbukan yang membentuk kawah Chicxulub dan banjir lava basal di Dekan yang muncul 65 juta tahun silam. Dan yang membedakannnya lagi, pembentukan Struktur Logoisk (diameter 17 km) dengan vulkanisme basalt Afro Arabia di Yaman pada 30 juta tahun silam ini 'hanya' menyemburkan 30 milyar ton gas sulfurdioksida, belum seberapa dibandingkan massa 8.000 milyar ton gas SO2 yang disemburkan Chicxulub (diameter asli 300 km) dan vulkanisme Dekan pada 65 juta tahun silam, event yang diyakini menghasilkan peristiwa pemusnahan massal dimana 75 % populasi makhluk hidup tersapu dari muka Bumi, termasuk kadal raksasa alias dinosaurus.

Dan satu lagi yang membedakan, bila kejadian 65 juta tahun silam berada dalam sistem podal-antipodal planet Bumi (silahkan direkonstruksikan posisi Kawah Chicxulub dan pusat semburan banjir lava basalt Dataran Tinggi Dekan pada 65 juta tahun silam, maka akan kita dapatkan kawah raksasa produk tumbukan benda langit berdiameter minimal 10 km tersebut tepat berada di titik lawan (antipodal) pusat banjir lava basalt Dekan dalam globe Bumi), Struktur Logoisk dengan pusat vulkanisme basalt Afro Arabia tidaklah demikian. Sehingga tidak jelas benar apakah tumbukan Logoisk yang memicu aktivitas vulkanisme basalt Afro Arabia, atapun meningkatkan intensitas aliran lava dari mantel Bumi. Sebagai pembanding, dalam kejadian 65 juta tahun silam, aktivitas vulkanisme basalt di Dataran Tinggi Dekan telah berlangsung lebih dulu dibanding kejadian tumbukan Chicxulub. Namun tumbukan benda langit tersebut menghasilkan gelombang seismik cukup kuat yang di titik antipodal
kawah tumbukan terkumpul (terfokuskan) kembali dan memanaskan lapisan selubung Bumi setempat secara adiabatik, sehingga meningkatkan aliran keluar lava basalt di Dataran Tinggi Dekan. Volume banjir lava basalt kian membesar ketika -- ini masih hipotesis -- di dekat pusat semburan lava ini pun terbentuk kawah tumbukan raksasa berdiameter 600 km (!) yang kita kenal sebagai Struktur Shiva.

So, inilah mekanisme pemusnahan massal itu. Ketika komet/meteor raksasa (dengan diameter minmal 10 km) jatuh membentur permukaan Bumi, gelombang seismik yang diproduksinya cukup kuat untuk terfokuskan kembali pada titik antipodalnya, dan memicu aktivitas vulkanisme areal berupa banjir lava basalt di sana. Kombinasi emisi gas CO2 dan SO2 yang dihembuskan dari kedua peristiwa tersebut, disamping debu2 vulkanik dan mikrotektit produk tumbukan yang menggelapkan atmosfer, itulah yang mengiamatkan kehidupan di permukaan Bumi, sebagaimana terjadi pada 250 juta tahun silam dan 65 juta tahun silam.

Salam,

Ma'rufin

----- Forwarded Message ----
Subject: Catastrophic Coincidence: Second Ever Example Of Contemporaneous Meteorite Impact And Flood Volcanism Discovered

Catastrophic Coincidence: Second Ever Example Of Contemporaneous Meteorite Impact And Flood Volcanism Discovered
ScienceDaily (Jan. 7, 2009) — Scientists have discovered only the second example of a meteorite
impact that occurred at the same time as massive volcanic activity, in
research published in the Journal of the Geological Society the week of
Jan 12. The first time such a coincidence was observed, at the
Cretaceous-Tertiary boundary, was the catastrophic event thought to be
responsible for the extinction of the dinosaurs, 65 million years ago.
This new event, uncovered after the 17 km diameter Logoisk impact
structure in Belarus was precisely dated, is thought to have taken
place around 30 million years ago. The crater was dated using argon
isotopes, and found to have occurred at a similar time to a period of
massive volcanism known as the Afro-Arabian flood volcanism, which
started in NW Yemen at around 30.9 Mya, and SW Yemen at around 29.0
Mya.
The impact also coincides broadly with a period of sudden global
cooling and sea level fluctuation. The researchers, led by Sarah
Sherlock at the Open University, argue that massive volcanic eruptions
and meteorite impacts are likely to have coincided much more frequently
than has previously been thought, but because the preservation of
impact craters on Earth is poor much of the evidence for these
coincidences is lost.
The relationships between meteorite impact craters, volcanism and
changes in climate is a subject of much debate among scientists. Prior
to the study, only one example of an impact coinciding with volcanism
had been found: the Chicxulub and Boltysh impacts and the Deccan Traps
flood volcanism, all of which occurred at the Cretaceous-Tertiary
boundary. In 2002, the discovery of their coincidence with a global
mass extinction led to debate over the causative links between
meteorite impacts, volcanism and mass extinction events, and fuelled
the search for more impacts at stratigraphic boundaries.
Unlike the Cretaceous-Tertiary event, the combination of the Logoisk
impact and the Afro-Arabain flood volcanism does not seem to have
caused an extinction event. The researchers suggest that the reason for
this may be that the magnitude of the event was not sufficiently large
in comparison. Whilst the Chicxulub crater associated with the
extinction of the dinosaurs measures 170km in diameter and the Deccan
Traps released around (2-4) x106 km3 of lava, in comparison
the Logoisk impact structure measures 17km across and the Afro-Arabian
flood volcanism is around 1.2 x106 km3 in volume.
As a result, the effects of each event were likely to have been very
different. At the Cretaceous-Tertiary boundary, it is thought that one
of the deadly effects was the release of sulphur dioxide, either as
acid rain or in the stratosphere, where it would have prevented heat
from reaching the earth and caused massive global cooling. Around 8000
billion tons of SO2 are thought to have been released by the volcanism
and meteorite impact. In comparison, the Logoisk impact and the
Afro-Arabian volcanism are thought to have contributed only 30 billion
tons of SO2.
Meteorite impact craters are extremely difficult to date, but an
understanding of their age and frequency is crucial to attempts to
control the number of future impacts, as well as understanding the
links between impacts and other catastrophic events such as large
volcanic eruptions and mass extinctions. Around 90% of the Earth's
record of meteorite impacts is lost, and the researchers argue that
coincidences between impacts and flood volcanism are far from rare.
They suggest that, for every incidence of flood volcanism, at least one
crater the size of Logoisk is likely to form, although few such
coincidences are likely to be on a scale grand enough to bring about an
extinction event comparable with that which destroyed the dinosaurs.
________________________________

The
Geological Society of London (2009, January 7). Catastrophic
Coincidence: Second Ever Example Of Contemporaneous Meteorite Impact
And Flood Volcanism Discovered. ScienceDaily. Retrieved January 7, 2009, from http://www.scienced aily.com/releases/2009/ 01/090107085320. htm

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Messages in this topic (1)

2a.: APA YANG TERJADI ketika hujan turun ?

Posted by: "meta utami" meta_utami@yahoo.com meta_utami

Sun Jan 11, 2009 8:07 pm (PST)

hi yudi! ternyata kita ketemu di sini, ya mwha ha ha

sepengetahuan
meta, secara singkat pak indra noviandri pernah menjelaskannya watu
kita tpb. Meta coba terangkan seingat meta aja ya(kimia meta nggak
jago2 amat, mungkin ada yang bisa bantu lebih detil penjelasannya)

jadi,
tahu kan kalo di alam ini ada yang namanya sistem entropi, atau derajat
ketidakteraturan di alam semesta. Semakin besar entropinya, semakin
tidak teratur suatu sistem. Nah, proses kondensasi awan, ternyata
adalah proses eksoterm(melepas panas),
di mana entropinya
mengecil(sehingga awan semakin solid, semakin padat, semakin teratur).
Panas yang kita rasakan di sekitar kita itu adalah panas yang
dilepaskan awan ketika dia memadat.

kalo ga salah sih gitu yud... punteun, amatir banget penjelasannya.

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2b.: APA YANG TERJADI ketika hujan turun ?

Posted by: "er_erhanz" er_erhanz@yahoo.com er_erhanz

Mon Jan 12, 2009 1:09 pm (PST)

thanx bgt infox, Slam kmal ya? klw da info nu, krim lg yach!!!!
by de way, knp kondensasi awan yg udah solid bs melayang teratus
(konstan)pd satu titik, g brtabrakan jd gumpalan yg lbih besar ya??
kyak teori planet awal(besarnya relatif sama)......?? pusing
gue...Hehehehe

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2c.: Re: APA YANG TERJADI ketika hujan turun ?

Posted by: "erika nurhansyah" er_erhanz@yahoo.com er_erhanz

Mon Jan 12, 2009 1:09 pm (PST)

klw mnurut ilmu pengawuranqyu sih gini....
udara yang panas(suhu tinggi) masa jenisnya kecil akan bergerak naik karena lebih ringan dr udara yg lbih dingin.

pas sampai di atas, udara kan reuni berkumpul bareng tmen2nya, lha terjadilah persekutuan(penggumpalan/kondensasi) awan.

karena tlah menjadi mendung dan memadat lagi jadi air,,,,ada lapisan air yang partikelnya padat.

Trus udara panas dari Bumi tercinta masih truz naik, eH Mentok di lapisan Mendung basah tadi, jadi udara panas terkungkung.
.......makanya kita merasa sumuk, ongkep atau bahasa kerennya kegerahan. HAAHAHAHAHA.

..........................Don't Try This at Home..............................

________________________________
From: myquantum07 <myquantum07@yahoo.com>
To: fisika_indonesia@yahoogroups.com
Sent: Saturday, January 10, 2009 9:24:52 PM
Subject: [FISIKA] APA YANG TERJADI ketika hujan turun ?

> to fisika_ers
> permisi Mas, Mbak... saya mau nanya...
kenapa pada saat turun hujan udara biasanya terasa panas ?
Bagaimana dengan tekanan dan kadar uap nya?????
> Tolong ya...
> Makasih.

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