Create a timeline which summarises the events mentioned in this text
Input: Explorers have been travelling to the Antarctic since the early 1900s. Shackleton was the first to cross the continent in 1914, but the colonial powers - Argentina, Chile and Great Britain - established their presence there in 1904.
1904: 
    * Colonial powers Argentina, Chile and Great Britain establish their presence in the Antarctic.
1914: 
    * Shackleton becomes the first explorer to cross the Antarctic continent.
1920:
    * Animal protection laws are enacted in some countries.
1921: 
    * Shackleton conducts his second and third expeditions to the Antarctic.
1922:
    * The first definite evidence of human inhabitation in the Antarctic Circle is found.
1969: 
    * The first unmanned Soviet expedition to the Antarctic arrives.
1985: 
    * The first multinational research station is set up in the Antarctic Peninsula.
1990: 
    * The Antarctic Treaty is signed.
1998: 
    * Encampment of refugees near the Amundsen–Scott South Pole Station.
The timeline would look as follows: 

1904 - Colonial powers Argentina, Chile and Great Britain establish their presence in the Antarctic 
2
1914 - Shackleton is the first person to cross the Antarctica
3
1948 - First official Antarctic Treaty signed 
4
1975 - U.S. publicly recognizes Antarctic environmental development 
5
1991 - Second Antarctic Treaty adopted 
6
1994 - UN Environment Programme becomes a consultative partner to the Antarctic Treaty 
7
1994 - Barcelona Convention for the protection of the Mediterranean Sea