Page 76 - D:\Video IPSyoFS22\

Changes in landscape of Anak Krakatau after eruption December 2018 and geochemical
characteristics of tephra

1
2
*
1 Ginting Frisa Irawan, Rudiyanto, Fiantis Dian

1 Program of Crop Science, Faculty of Fisheries and Food Science, Universiti Malaysia Terengganu,
21030 Kuala Nerus, Terengganu, Malaysia
2 Department of Soil Science, Faculty of Agriculture, Andalas University,
Padang 25175, Sumatera Barat, Indonesia

* Corresponding author: dianfiantis@yahoo.com

Abstract:

The South-western slope of Anak Krakatau volcano collapsed after the eruption on December 22 , 2018,
nd
resulting on the formation of a new landscape in the volcanic island. This study aims to determine the
morphological changes Anak Krakatau volcano before and after the eruption and geochemical
characterization of volcanic materials. The intensive activities and morphological changes of Anak
Krakatau were monitored using multi-sensor satellite imagery. To determine geochemical characterization
of tephra, a total of 60 lapilli and 23 volcanic ash samples were collected from Anak Krakatau and Panjang
island on March 14, 2019. The results showed that after the December 2018 eruption, the height of Anak
7
Krakatau was reduced from 338 to 148 m and about 7,6 x 10 m of materials were collapsed to the sea.
3
The Anak Krakatau area enlarged from 288 ha to 309 ha. By using satellite images 214 rills and 35 of the
gully features run from the highest peak to the coastline were identified. The temperature of lava was 195 C
o
based on MODIS satellite. The geochemical characteristics of the volcanic material were basaltic, basalt-
andesitic and andesitic which have a total elemental oxide content CaO > MgO > SO 4 > P2O5 > K2O. The
pH values were range from 4.52 to 7.32. The value of cations was in the decreasing order of Mg > Ca > Na
> K, but the CEC value was very low. Macronutrient reserves from the volcanic material of Anak Krakatau
were predicted to last from 4,778 to 1,033,199 years. The results of this study can provide geochemical
information on the positive aspects of volcanic ash and volcanic materials after the eruption which have a
high capability to supply nutrients to plants and the environment, respectively.

Keywords: Remote sensing, Volcanic materials, X-ray fluorescence, Nutrient reserves